Light source drive, optical information recording apparatus, and optical information recording method

ABSTRACT

A light source drive which modulates a light source so as to cause the same to emit a light, includes: a superposition current generation part which generates a superposition current approximately corresponding to a charging/discharging current needed for a capacitance occurring in parallel to the light source for a predetermined time period near at least one of a rising-up part and a decaying-down part of a waveform of a drive current for the light source; and an addition/subtraction part which adds to or subtracts from the drive current the superposition current generated by the superposition current generation part.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a light source drive whichdrives a semiconductor laser or so which is a light source used in anoptical disk drive or an optical information recording apparatus, suchas a CD-R drive, a CD-RW drive, a DVD-R drive, a DVD-RW drive, a DVD+RWdrive, a DVD-RAM drive, or so, such an optical information recordingapparatus, and an optical information recording method applied therein.

[0003] 2. Detailed Description of the Related Art

[0004] Conventionally, in an optical disk drive, a light source such asa semiconductor laser light source (laser diode or LD) which is a lightsource is appropriately modulated so as to emit a laser beam, which isapplied to an optical information recording medium (optical disk), andthus, information recording and information reproduction are performedthereon. For example, in a phase-change type optical disk used as aCD-RW disk, a DVD+RW disk, etc., an amorphous state, i.e., a recordingmark, is formed by increasing the temperature of therecording medium tomore than the melting point thereof, and carrying out a sudden coolingthereof so that it is cooled within the crystallization time of therecording medium.

[0005] That is, in order to form a properly-shaped record mark and wellcontrol the position thereof on the recording medium such as an opticaldisk, the beam application energy and time duration thereof should becontrolled correctly, and it is necessary to generate an exact lightwaveform in the laser beam. Especially, in case high-speed informationwriting is required, a control of the characteristic of rising-up anddecaying-down of the light waveform is an essential matter.

[0006] For example, in a write-once disk employing a pigment such as aCD-R disk, a DVD+R disk, etc., a record mark is formed by producing athermal deformation occurring from a beam-application or a substratetransformation occurring therefrom so as to cause an opticaltransformation there.

[0007] Accordingly, in order to achieve a proper record mark formationand a position control thereof, it is necessary to generate an exactlight waveform in the laser beam applied onto the optical recordingmedium.

[0008] According to Japanese laid-open patent application No. 10-308026,for example, in case of employing a pulse series for driving a laser forwell controlling a recording area of an optical recording medium, asnubber circuit is applied so as to absorb a starting power occurringdue to a parasitic inductance. Thereby, it is possible to preventovershooting or ringing otherwise occurring in a laser driving beamwaveform due to the parasitic inductance included in a circuit used fortransmitting the driving signal up to the laser with high-frequencycomponents included in the pulse series.

[0009] With regard to other types of optical recording media such as MOor MD for which a magnetic inversion phenomenon occurring near the Curiepoint is utilized, the same situation occurs.

[0010] In such a conventional light source drive described above, thefollowing problems to be solved are involved. FIG. 1 illustrates theproblem occurring in a case of driving an LD (laser diode) in aconventional light source drive. FIG. 2 shows waveforms in case the LDis driven by the light source drive shown in FIG. 1.

[0011] In FIG. 1, in order to simplify the description, in an LD drivepart 201, illustration is omitted except a source of current whichsupplies a drive current.

[0012] Generally speaking, some amount of junction capacitance occursbetween an anode and a cathode of the LD (in addition, a parasiticcapacitance also occurs there). In the figure, the reference numeral 203indicates a simple LD equivalent model in consideration of this junctioncapacitance.

[0013] ‘CLD’ in this LD equivalent model 203 indicates theabove-mentioned junction capacitance (the above-mentioned parasiticcapacitance is also included therein), ‘r’ indicates an ON resistance,and ‘LDi’ indicates an ideal LD. Due to the occurrence of the junctioncapacitance, even when a predetermined drive current is provided with asharp rising-up and a sharp decaying-down in its waveform, i.e., of arectangular waveform, as shown in FIG. 2A, a part of the current is toflow through the junction capacitance as a charging/discharging currentIc therefor. Accordingly, the current then flowing through the ideal LD(LDi) has not sufficiently sharp rising-up and decaying-down, i.e.,rounded, as shown in FIG. 2B. As a result, it becomes not possible todrive the LD with a desired signal waveform such as that shown in FIG.2A.

[0014] Thereby, it may not be possible to produce a precisely shapedrecord mark or a well controlled mark position on a relevant opticalrecording medium, and, thus, the data recording may include data errorsaccordingly.

[0015] Especially, in case of achieving high-speed recording ofinformation onto an optical recording medium, an output of the LD shouldbe increased accordingly. However, generally speaking, a high-output LDhas a large junction capacitance, and, also, in this case, high-speedrising-up and decaying-down of signal waveform is essential.Accordingly, the above-mentioned problem of possible data errorgeneration due to degradation in the signal waveform rising-up anddecaying-down performance may become remarkably worse. This problem isreferred to as a first problem.

[0016] Moreover, generally speaking, a transmission line 202 whichprovides the drive current from the LD drive part 201 to the LD isinstalled usually on a flexible printed circuit board (FPC), and in thetransmission circuit 202, as shown in FIG. 1, parasitic inductances Lp1and Lp2 and parasitic capacitances Cp1 and Cp2 may occur.

[0017] In case a high-speed modulation or driving of the LD is carriedout, the signal of a high-frequency component causes a resonancephenomenon with these parasitic inductances etc. As a result, the drivecurrent includes overshooting or ringing, as shown in FIG. 2C, and then,it may become not possible to achieve generation of a light beam with adesired waveform from the LD. Accordingly, record marks thus formed onthe optical recording medium may not have proper shapes norwell-controlled positions, and, thus, as mentioned above, data errorsmay occur at a time when information reproduction is made from therecording medium. This problem is referred to as a second problem.

[0018] The above-mentioned first and second problems may occursimultaneously in combination in some cases.

SUMMARY OF THE INVENTION

[0019] A first purpose of the present invention is to solve theseproblems. Specifically, the first purpose is to control a distortion (adelay or a degradation in rising-up or decaying-down characteristics)otherwise occurring in a waveform of a light beam emitted from a lightsource such as an LD due to a junction capacitance of the LD, parasiticinductances of the transmission circuit, and, thus, to achieve ageneration of the light beam with a desired waveform by solving theseproblems.

[0020] Moreover, the following problems may also occur when a high-speedoperation is attempted in an optical disk derive. In an optical diskdrive, since a high-speed operation and a high integration orminiaturization of the device have been demanded, a micro-fabricatedCMOS process is considered advantageous to be applied therefor.

[0021] On the other hand, in such an LD drive, since a light source LDhaving an operation voltage in a range of 1 through several volts isconnected thereto, a high-voltage process (for example, 5 volts, 3.3volts or so) is also needed.

[0022] However, usually, in a micro-fabricated CMOS process, it isdifficult to achieve such a high-voltage process. For example, a CMOSprocess of 0.18 μm has a withstand voltage of as high as 1.8 volts.Accordingly, it may become not possible to achieve high-speed operation,or, even it is possible, a considerable price increase, an increase inconsumption power, an increase in size or so may occur for achieving thehigh-speed operation.

[0023] One scheme of controlling a signal for driving an LD acting as alight source will now be discussed for illustrating another problem tobe solved. In this scheme, for example, predetermined modulation signalsM0, M1 and M2 are generated according to predetermined drive waveformgeneration information held in driving waveform generation informationstorage in a modulation signal generation unit. Then, respectiveswitches are provided for these modulation signals M0, M1, M2, . . . ,and are appropriately controlled. Thereby, one or some thereof areselected, and, after that, the thus-selected signals are made to undergoan operation by means of an adder and a current drive part. Thereby, amulti-level drive current signal is produced from these signalsthus-selected, and is provided to the LD. Thereby, the LD emits amulti-level laser beam. In this scheme, a delay amount control part isprovided for generating signal difference amounts by which differencesotherwise occurring among these source signals M0, M1, M2, . . . ,should be controlled appropriately.

[0024] In this scheme, it is possible to reduce a distortion from adesired optical modulation waveform due to a signal distortion or a skewoccurring in a modulation signal waveform. Accordingly, it becomespossible to employ a micro-fabricated CMOS process to theabove-mentioned modulation signal generation unit which seeks high-speedoperation and high integration or miniaturization of device. Also, it ispossible to produce a signal processing part, controller and so forthneeded in a light source drive into a single integrated circuit.Accordingly, it becomes possible to reduce the total manufacturingcosts.

[0025] In this case, a problem occurring due to a skew occurring amongthe respective modulation signals, or so, in case of signal transmissionvia the FPC substrate can also be solved.

[0026] Further, in order to solve the above-mentioned first and secondproblems in a scheme in which the above-mentioned modulation signalgeneration unit and the LD drive part are provided separately, asuperposition current generation part may be provided for providing apredetermined overshoot current and a predetermined undershoot current,by which possible overshooting and undershooting amounts in a modulationsignal such as those shown in FIG. 2C are cancelled out.

[0027] However, when this superposition current generation part isprovided together with the modulation signal generation part in a singleintegrated circuit (IC) for the purpose of price reduction andimprovement in the manufacturing accuracy, different from a case of anintegrated circuit containing the LD drive part, a problem may occur.That is, as superposition signals provided by the superposition currentgeneration part should be transmitted to the LD drive part together withthe modulation signals provided by the modulation signal generationpart. Accordingly, for the purpose of transmission of these signals, theFPC substrate used therefor should have a larger width, and, also, theintegrated circuit should have an increased number of interface pins.Accordingly, price reduction and miniaturization of the system may beobstructed.

[0028] Accordingly, a second object of the present invention is toachieve a miniaturization and a price reduction of the light sourcedrive, while the light source drive should emit a light beam with adesired signal waveform (or light waveform) by solving the problem ofdegradation of the light waveform otherwise occurring due to a delay inrising-up/decaying-down (or edge rounding) or ringing of waveform whichmay otherwise occur due to the junction capacitance of the LD or theparasitic inductance of the transmission circuit.

[0029] A light source drive according to the present invention whichmodulates a light source so as to cause the same to emit a light,includes: a waveform shaping part which corrects a deformation of alight waveform of the light to be emitted from the light source.

[0030] A light source drive according to another aspect of the presentinvention which modulates a light source so as to cause the same to emita light, includes: a superposition current generation part whichgenerates a superposition current approximately corresponding to acharging/discharging current needed for a capacitance occurring inparallel to the light source for a predetermined time period near atleast one of a rising-up part and a decaying-down part of a waveform ofa drive current of the light source; and an addition/subtraction partwhich adds to or subtracts from the drive current the superpositioncurrent generated by the superposition current generation part.

[0031] A light source drive according to another aspect of the presentinvention which modulates a light source so as to cause the same to emita light, includes: an output impedance control part which changes anoutput impedance value of a drive current output part which provides adrive current to the light source, for a predetermined time period nearat least one of a rising-up part and a decaying-down part of a waveformof the drive current.

[0032] A light source drive according to another aspect of the presentinvention which modulates a light source so as to cause the same to emita light, includes: a MOS transistor connected in parallel with a drivecurrent output part which outputs a drive current to the light source;and a voltage control part which applies a voltage to a gate of the MOStransistor such that the MOS transistor enters a linear region for apredetermined time period near at least one of a rising-up part and adecaying-down part of a waveform of the drive current.

[0033] A light source drive according to another aspect of the presentinvention which modulates a light source so as to cause the same to emita light, includes: a superposition current generation part whichgenerates a superposition current approximately corresponding to acharging/discharging current needed for a capacitance occurring inparallel to the light source for a predetermined time period near atleast one of a rising-up part and a decaying-down part of a waveform ofa drive current of the light source; an addition/subtraction part whichadds to or subtracts from the drive current the superposition currentgenerated by the superposition current generation part; and an outputimpedance control part which changes an output impedance value of adrive current output part which provides the drive current to the lightsource, for a predetermined time period near at least one of a rising-uppart and a decaying-down part of a waveform of the drive current.

[0034] A light source drive according to another aspect of the presentinvention which modulates a light source so as to cause the same to emita light, includes: a superposition signal generation part whichgenerates a superposition signal which indicates a predetermined timeperiod near at least one of a rising-up part and a decaying-down part ofa waveform of a drive current of the light source; a superpositioncurrent generation part which generates a superposition currentapproximately corresponding to a charging/discharging current needed fora capacitance occurring in parallel to the light source based on thesuperposition signal generated by the superposition signal generationpart; an addition/subtraction part which adds to or subtracts from thedrive current the superposition current generated by the superpositioncurrent generation part; and an output impedance control part whichchanges an output impedance value of a drive current output part whichprovides the drive current to the light source, for a predetermined timeperiod near at least one of a rising-up part and a decaying-down part ofa waveform of the drive current.

[0035] A light source drive according to another aspect of the presentinvention which modulates a light source so as to cause the same to emita light, includes: a waveform shaping part which corrects a deformationof a light waveform of the light to be emitted from the light source;and a waveform shaping time control part which controls a time periodfor which the waveform shaping part performs a waveform shapingoperation.

[0036] A light source drive according to another aspect of the presentinvention includes: a light source modulation part which modulates alight source so as to cause the same to emit a light; a superpositioncurrent generation part which generates a superposition current in apredetermined amount for a predetermined time period near at least oneof a rising-up part and a decaying-down part of a waveform of a drivecurrent of the light source; an addition/subtraction part which adds toor subtracts from the drive current the superposition current generatedby the superposition current generation part; and a superposition timecontrol part which controls the predetermined time period so as to causeit to have a predetermined value.

[0037] A light source drive according to another aspect of the presentinvention includes: a light source modulation part which modulates alight source so as to cause the same to emit a light; an outputimpedance control part which changes an output impedance value of thelight source modulation part for a predetermined time period near atleast one of a rising-up part and a decaying-down part of a waveform ofa drive current of the light source; and a time control part whichcontrols the predetermined time period so as to cause it to have apredetermined value.

[0038] A light source drive according to another aspect of the presentinvention includes: a light source modulation part which modulates alight source so as to cause the same to emit a light; a superpositioncurrent generation part which generates a superposition current in apredetermined amount for a first predetermined time period near at leastone of a rising-up part and a decaying-down part of a waveform of adrive current of the light source; an addition/subtraction part whichadds to or subtracts from the drive current the superposition currentgenerated by the superposition current generation part; an outputimpedance control part which changes an output impedance value of thelight source modulation part for a second predetermined time period nearat least one of a rising-up part and a decaying-down part of a waveformof a drive current of the light source; and a time control part whichcontrols the first predetermined time period and the secondpredetermined time period so as to cause them to have predeterminedvalues.

[0039] Thus, according to the present invention, a distortion of a lightwaveform otherwise occurring due to a junction capacitance of an LD, aparasitic inductance of transmission circuit, or so, can be correctedwith a simple configuration, and thereby, a laser beam is produced witha desired light waveform, effectively. Further, it is also possible toeffectively miniaturize or reduce in price of an optical informationrecording apparatus while fine control of light waveform of a laser beamapplied to an optical recording medium is maintained at a high grade.

[0040] An optical information recording method of forming a record markon a recording medium by applying a light emitted from a light source ina form of a pulse series according to the present invention, includesthe steps of: a) adding a pulse of predetermined power for apredetermined time period after near a rising-up part of at least somepulses of the pulse series; and b) controlling a pulse width of thepulse thus added so as to control the formation of the record mark.

[0041] An optical information recording method of forming a record markon a recording medium by applying a light emitted from a light source ina form of a pulse series according to another aspect of the presentinvention, includes the steps of: a) adding a first addition pulse ofpredetermined power for a predetermined time period after near arising-up part of at least some pulses of the pulse series; b) adding asecond addition pulse of predetermined power for a predetermined timeperiod after near a decaying-down part of the at least some pulses ofthe pulse series; and c) controlling a pulse width of the first additionpulse thus added and a pulse width of the second addition pulse thusadded so as to control the formation of the record mark.

[0042] An optical information recording method of forming a record markon a recording medium by applying a light emitted from a light source ina form of a pulse series according to another aspect of the presentinvention, includes the steps of: a) adding or subtracting apredetermined addition current to a drive current of the light sourcefor a predetermined time period after near a rising-up part or adecaying-down part of at least some pulses of the pulse series; b)determining the predetermined time for the addition current such thatpart of the addition current is approximately appropriated forcharging/discharging a capacitance occurring in parallel to the lightsource and the remaining part of the addition current is used as anaddition power to be applied, so as to control the formation of therecord mark.

[0043] An optical information recording apparatus according to thepresent invention for forming a record mark on a recording medium byapplying a light emitted from a light source in a form of a pulseseries, includes: an addition current generation part which generates anaddition current in a predetermined value for a predetermined timeperiod after near a rising-up part of at least some pulses of the pulseseries; an addition time setting part which determines the predeterminedtime period for the addition current; and an adding part which adds theaddition current to a drive current of the light source.

[0044] An optical information recording apparatus according to anotheraspect of the present invention for forming a record mark on a recordingmedium by applying a light emitted from a light source in a form of apulse series, includes: an addition current generation part whichgenerates an addition current in a predetermined value for apredetermined time period after near a rising-up part or a decaying-downpart of at least some pulses of the pulse series; an addition timesetting part which determines the predetermined time period for theaddition current; and an adding/subtracting part which adds/subtractsthe addition current to a drive current of the light source.

[0045] An optical information recording apparatus according to anotheraspect of the present invention for forming a record mark on a recordingmedium by applying a light emitted from a light source in a form of apulse series, includes: an addition current generation part whichgenerates an addition current in a predetermined value for apredetermined time period after near a rising-up part or a decaying-downpart of at least some pulses of the pulse series; an addition timesetting part which sets the predetermined time for the addition currentsuch that part of the addition current is approximately appropriated forcharging/discharging a capacitance occurring in parallel to the lightsource and the remaining part of the addition current is used as anaddition power to be applied; and an adding/subtracting part whichadds/subtracts the addition current to a drive current of the lightsource.

[0046] Thus, according to the present invention, it becomes alsopossible to effectively increase the resolution of beam-applicationenergy so as to achieve fine control of record mark formation even incase of high-speed recording, without increasing the time-axisresolution in a beam-application time duration or in a cooling timeduration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIG. 1 illustrates a problem in a case of driving an LD with aconventional light source drive;

[0048]FIGS. 2A, 2B and 2C show light waveforms in an example when an LDis driven with the light source drive shown in FIG. 1;

[0049]FIG. 3 shows a block diagram of a configuration of a light sourcedrive according to a first embodiment of the present invention;

[0050]FIG. 4 shows waveforms of signals occurring in the light sourcedrive according to the first embodiment of the present invention;

[0051]FIG. 5 shows a block diagram of a configuration of a light sourcedrive according to a second embodiment of the present invention;

[0052]FIG. 6 shows a circuit diagram for illustrating operation ofcontrolling a ringing of a light waveform otherwise occurring due to aparasitic inductance which is the second problem occurring in aconventional light source drive;

[0053]FIG. 7 shows another example of a configuration of a variableresistance part which may be applied to the second embodiment of thepresent invention;

[0054]FIGS. 8A, 8B and 8C show another example of the variableresistance part, a waveform of an output signal thereof, and an Id-Vdscharacteristic of a MOS transistor shown in FIG. 8A, respectively;

[0055]FIG. 9 shows a block diagram of a configuration of a light sourcedrive according to a third embodiment of the present invention;

[0056]FIG. 10 shows a block diagram of a configuration of a light sourcedrive according to a fourth embodiment of the present invention;

[0057]FIG. 11 shows a block diagram of detailed internal configurationsof a superposition signal generation part and a superposition timecontrol part shown in FIG. 10;

[0058]FIG. 12 shows examples of waveforms of signals occurring in theconfiguration shown in FIG. 11;

[0059]FIG. 13 shows an example of a characteristic of an oscillationfrequency with respect to a frequency setting current in an oscillatorshown in FIG. 11;

[0060]FIG. 14 shows examples of waveforms of signals for illustrating aprocessing for a measurement of an oscillation frequency of theoscillator shown in FIG. 11;

[0061]FIG. 15 shows a block diagram of a configuration of a light sourcedrive according to a fifth embodiment of the present invention;

[0062]FIG. 16 illustrates an operation for controlling a ringing of alight waveform otherwise occurring due to a parasitic inductance, whichis the second problem to be solved;

[0063]FIG. 17 shows another internal configuration of a variableresistance part shown in FIG. 15;

[0064]FIG. 18 shows a configuration of a light source drive according toa sixth embodiment of the present invention;

[0065]FIG. 19 illustrates a problem occurring in a case of driving an LDwith a conventional light source drive;

[0066]FIG. 20 shows light waveforms in an example when an LD is drivenwith the light source drive shown in FIG. 19;

[0067]FIG. 21 shows a block diagram of a configuration of a light sourcedrive of an optical information recording apparatus according to aseventh embodiment of the present invention;

[0068]FIG. 22 shows waveforms of signals occurring in the light sourcedrive according to the seventh embodiment of the present invention;

[0069]FIG. 23 shows waveforms illustrating a relationship between aheating pulse having an addition power added thereto and abeam-application energy occurring therefrom; and

[0070]FIG. 24 shows waveforms of an LD drive current and a lightwaveform for illustrating operation of the seventh embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0071] Hereafter, embodiments of the present invention will bespecifically described based on the drawings.

[0072] A first embodiment of the present invention will now bedescribed.

[0073]FIG. 3 is a block diagram showing a configuration of a lightsource drive according to the first embodiment of the present invention.The light source drive according to the first embodiment is directed tosolve the above-mentioned first problem. Moreover, FIG. 4 shows awaveform showing an example of each signal occurring in the light sourcedrive according to the first embodiment.

[0074] The light source drive 1 includes a beam-application levelsetting part 2 which sets beam-application levels P0, P1, and P2 of anLD as shown in FIG. 3 (beam-application level control part). Amodulation signal generation part 4 also included in the light sourcedrive 1 generates modulation signals Mod1 and Mod2 for the LD from arecord data signal Wdata and a record clock signal WCK. Further, amodulation part 3 also included in the light source derive 1 generatesan LD modulation current Imod based on beam-application level dataP0Data, P1Data, P2Data corresponding to the beam-application levels P0,P1, and P2 of the LD, respectively, and the modulation signals Mod1 andMod2.

[0075] A superposition current generation part 18 generates an overshootcurrent Ios and an undershoot current Ius which are superpositioncurrents based on modulation timings (which correspond to rising-up ordecaying-down timings of the modulation signals Mod1 and Mod2, or totheir parts) which the modulation signal generation part 4 generates. AnLD control part 7 also shown controls a bias current Ibias and a scalesignal Iscl which indicates a scale of a modulation current so that alight emission amount of the LD becomes a desired value based on amonitored light-receiving signal, which is input from a monitoring PDwhich monitors a part of the emitted light of the LD.

[0076] An addition-and-subtraction part 5 also shown adds the LDmodulation current Imod and the bias current Ibias together, furtheradds thereto the overshoot current Ios, and subtracts the undershootcurrent Ius therefrom. A current drive part 6 amplifies a current ILD′thus produced by the addition-and-subtraction part 5 and provides adrive current ILD to the LD. A control part 17 receives control commandsprovided by a controller 19 which controls the entirety of aninformation recording apparatus which includes the above-mentioned lightsource drive 1, and provides control signals to the respective parts.

[0077] Next, a detailed internal configuration of the modulation part 3will now be described. The modulation part 3 includes a source 8 ofcurrent which supplies currents I0, I1, and I2 based on thebeam-application level data P0Data, P1Data, and P2Data, respectively,which source actually includes respective current sources P0DAC 8 a,P1DAC 8 b, and P2DAC 8 c. Switches 9 b and 9 c carry out an on-offcontrol of the currents I1 and I2 according to the modulation signalsMod1 and Mod2, respectively, and an addition part 10 which adds eachcurrent together which the switches 9 output, and thus supplies an LDmodulation current Imod.

[0078] Next, a detailed internal configuration of the superpositioncurrent generation part 18 will now be described. The superpositioncurrent generation part 18 includes a superposition signal generationpart 11 which generates superposition signals (respectively, ModO andModU) which specify periods for which the overshoot current Ios andundershoot current Ius are superposed based on the modulation timingswhich the modulation signal generation part 4 generates, respectively. Asuperposition current value setting part 16 sets current values 13 and14 of the overshoot current Ios and undershoot current Ius, and suppliessetting data OSData and USData.

[0079] Current sources OSDAC 13 a and USDAC 13 b supply the currents I3and I4 based on the overshoot current setting data OSData and theundershoot current setting data USData, respectively. Switches 14 a and14 b carry out an on-off control of the currents 13 and 14 according tothe superposition signals ModO and ModU, respectively, and generate theovershoot current Ios and the undershoot current Ius. A superpositiontime setting part 15 sets respective superposition times for theovershoot current Ios and undershoot current Ius.

[0080]FIG. 4 shows a waveform in an example of a main signal of eachpart shown in FIG. 3. This figure shows a case at a time of recordinginformation to a phase-change type recording medium. In FIG. 4, awaveform (c) is a desired light waveform, and record marks shown in (d)are formed from application of this light waveform. Levels Pb, Pe, andPw of the light waveform (c) are respective beam-application levels of abottom power level, an erase power level, and a light power level,respectively, and are beam-application levels for which the current ILD′is set to (Ibias+I0), (Ibias+I0+I1), and (Ibias+I0+I2), respectively.That is, the beam-application level is determined by thebeam-application level data P0Data, P1Data, and P2Data, which set thecurrent values I0, I1, and I2, respectively.

[0081] The modulation signals Mod1 (e-1) and Mod2 (e-2) in FIG. 4 aregenerated corresponding to the record data Wdata (b) based on drivewaveform information that indicates desired modulation timing of thelight waveform beforehand set in the modulation signal generation part4.

[0082] The superposition signal ModO (f-1) shown in FIG. 4 is generatedso as to have a high level only during the superposition time periods(To1, To2, To3) for the overshoot current according to instructionscoming from the superposition time setting part 15 in synchronizationwith the rising-up of the modulation signal Mod1 or Mod2, in thesuperposition signal generation part 11. Thereby, the overshoot currentIos is generated and is added to the LD drive current.

[0083] Similarly, the superposition signal ModU (f-2) shown in the samefigure is generated so as to have a high level only during thesuperposition time periods (Tu1) for the undershoot current according toinstructions coming from the superposition time setting part 15synchronized with the decaying-down of the modulation signal Mod2.

[0084] According to these modulation signals and superposition signals,the current ILD′ (g) is generated. The drive current ILD finallysupplied to the LD is obtained from appropriately amplifying theabove-mentioned current ILD′ via an amplifier 6.

[0085] That is, the current waveform is obtained superposed with theovershoot current Ios at the time of the rising-up of drive current,while superposed with the undershoot current Ius at the time ofdecaying-down thereof. Current levels I0 through I4 shown in the figureare current values generated in the current sources 8 and 13,respectively, and the current Ibias corresponds to a threshold currentof the LD provided by the LD control part 7.

[0086] The overshoot current Ios and the undershoot current Ius thusgenerated and superposed are used as charging/discharging currents forthe junction capacitance of the LD. Accordingly, a delay ofrising-up/decaying-down timing or rounding of the light waveform can beavoided. Accordingly, a light can be made to be emitted with a desiredlight waveform from the LD, and thus, exact record marks can be formedon the optical recording medium thereby.

[0087] The junction capacitance may differ according to a particularproduct of the LD applied. Accordingly, it is preferable that theabove-mentioned superposition current values should be preferablyadjusted accordingly. Thereby, appropriate charging/discharging of thejunction capacitance of the LD can be achieved, thus, a still more ideallight waveform can be obtained, and a more excellent record markformation can be performed. In the light source drive according to thefirst embodiment of the present invention, the superposition currentvalue setting part 16 executes this function. The same effect isacquired by adjusting the superposition time of overshoot current Iosand undershoot current Ius, instead. In the light source drive of thefirst embodiment, the superposition time setting part 15 executes thisfunction. It is also possible to combine these functions.

[0088] Furthermore, it is further preferable to adjust the currentvalues and/or the superposition times of the overshoot current Ios andthe undershoot current Ius according to changes of beam-applicationlevel. That is, according to changes in the beam-application level,i.e., Pe→Pw, Pb→Pw, Pb→Pe, the amounts of change in the potential acrossthe cathode and anode of the LD differ, and thus, thecharging/discharging current needed changes accordingly. Therefore, whenthe superposition times (To1, To2, To3) are controlled according to thethus changing beam-application level shift, a delay of therising-up/delaying-down timing or rounding of the light waveform can becontrolled more finely. The same effect can be acquired by controllingthe current values.

[0089] Thus, according to the present embodiment, the waveform shapingdevice is provided to correct deformation occurring in light waveformresulting from the parasitic device occurring in the transmission linefor the light source or the light source itself, such as parasiticcapacitance or inductance. Accordingly, deformation (rounding ofrising-up or decaying-down waveform, or ringing) in the light waveformcan be well corrected, and thus, a light can be made to be emitted witha desired light waveform from the LD.

[0090] Moreover, according to the present embodiment, the superpositioncurrents corresponding to the charging/discharging currents required forthe capacitance occurring, in parallel, such as the junction capacitanceof the light source on the rising-up or decaying-down of the drivecurrent for the light source are superposed onto the drive current.Accordingly, the rising-up or decaying down of the light waveform can beprevented from being delayed or rounded otherwise occurring due to theabove-mentioned capacitance occurring in parallel to the light source.Therefore, when this scheme is applied to an optical informationrecording apparatus such as an optical disk drive, formation of exactrecord marks can be achieved.

[0091] Furthermore, according to the present embodiment, thesuperposition time for which the superposition current is superposedonto the drive current of the light source may be controlled accordingto the capacitance occurring in parallel with the light source asmentioned above. Thereby, a delay or rounding of the rising-up ordecaying-down of the light waveform can be appropriately cancelledaccording to a particular product of the light source applied. Thus, alight can be made to be emitted with a desired light waveform from theLD.

[0092] Moreover, according to the present embodiment, the superpositioncurrent value superposed to the drive current of the light source may becontrolled according to the capacitance occurring in parallel with thelight source. Thereby, according to the particular light source applied,a delay or rounding of the risingup/decaying-down of the light waveformcan be well cancelled, and light can be made to be emitted with adesired light waveform.

[0093] Furthermore, both the superposition times and the superpositioncurrent values, according to which the superposition current values aresuperposed on the drive current of the light source, may be controlledaccording to the capacitance occurring in parallel with the lightsource. Thereby, according to the light source applied, a delay orrounding of the rising-up/decaying-down of the light waveform can bewell cancelled, and light can be made to be emitted with a desired lightwaveform.

[0094] Moreover, the superposition times for which the superpositioncurrents are superposed to the drive current may be controlled accordingto the amount of change of the drive current of the light source.Thereby, a delay or rounding of the rising-up/decaying-down of the lightwaveform can be controlled more correctly.

[0095] Furthermore, the superposition current values superposed onto thedrive current may be controlled according to the amount of change of thedrive current of the light source. If so, a delay or rounding of therising-up/decaying-down of the light waveform can be controlled morecorrectly.

[0096] Next, a second embodiment of the present invention will now bedescribed.

[0097]FIG. 5 shows a block diagram showing a configuration of a lightsource drive according to the second embodiment of the presentinvention. The light source drive of this embodiment solves theabove-mentioned second problem. Each block having the same referencenumeral as that shown in FIG. 3 performs the same operation and functionas described, and, thus detailed description thereof will be omitted.

[0098] As shown in FIG. 5, in parallel with the source of current whichprovides the output current of the current drive part 6, a variableresistance part 21 is connected which controls the output impedance ofthe light source drive part 1. According to an impedance control signalModZ, this variable resistance part 21 has a resistance Rd according toa resistance value setting signal Svr when the ModZ=High, while this hasan approximately infinite resistance when the ModZ=Low.

[0099] A resistance setting part 22 generates the resistance settingsignal Svr which indicates a resistance for a case where the lowerimpedance is provided by the variable resistance part 21 as mentionedabove.

[0100] An impedance control signal generation part 20 starts up insynchronization with the modulation timing (which corresponds to therising-up or decaying-down timing of the modulation signals Mod1 andMod2, or a part thereof) supplied from the modulation signal generationpart 4, and generates the impedance control signal ModZ having a highvalue only during a period set by a dumping time setting part 23. Theseparts 20 through 23 execute a function of controlling the outputimpedance of the LD driver.

[0101]FIG. 6 shows a circuit diagram for illustrating control operationof a function of controlling a ringing of a light waveform occurring dueto a parasitic inductance, which corresponds to the above-mentionedsecond problem.

[0102] A ringing of the light waveform occurs due to a resonanceoccurring in a loop indicated by a broken arrow shown in FIG. 6. It iseffective to connect a resistance component to this loop in parallel, inorder to control or well reduce this resonance. The resistance componentshould just be connected at a time of the rising-up/decaying-down of thedrive current at which the ringing would otherwise occur. A currentsource 30 shown in FIG. 6 corresponds to a current source at an outputstage which supplies an output current in the current drive part 6 shownin FIG. 5.

[0103] A variable resistance part 31 shown in FIG. 6 achieves theabove-mentioned function, and the variable resistance part 21 shown inFIG. 5 corresponds thereto. This includes a switch 33 and a resistor 34,and an on-off control is carried out by the switch according to theimpedance control signal ModZ. In case the resistor 34 is made of avariable resistor for which the resistance thereof is set by theresistance setting signal Svr, and the resistance is set according tothe characteristic of the transmission circuit between the light sourcedrive part 1 and the LD, the ringing can thus be controlledappropriately and as a result a light can be made to be emitted with adesired light waveform.

[0104] Moreover, as the power supply VDD and the ground areshort-circuited in terms of AC operation, the variable resistance part32 may be connected as shown in FIG. 6.

[0105]FIG. 7 shows another example of the variable resistance part. Thisvariable resistance part has a parallel connection of resistors R1through Rn with switches SW1 through SWn connected in series therewith,respectively. One of the switch is selected according to the resistancesetting signal Svr, while an on-off control is performed on thethus-selected switch according to the impedance control signal ModZ.According to the thus-configured variable resistance part, it becomespossible to effectively control or well reduce the ringing suitablyaccording to the transmission circuit characteristic with a simpleconfiguration.

[0106]FIGS. 8A, 8B and 8C illustrate another example of the variableresistance part together with an output signal waveform thereof, and anId-Vds characteristic of a MOS transistor. In this example, as shown inFIG. 8A, in parallel with a current source 30, a variable resistancepart 40 including the MOS transistor 41 (here, it is of a p-channeltype) and a voltage control part 42 which controls the gate voltageVctrl of the MOS transistor 41 based on the impedance control signalModZ and the resistance setting signal Svr.

[0107] The MOS transistor 41 acts as a voltage controlled resistance,when the voltage Vds between the drain and source becomes lower than thepinch-off voltage (in the linear region) (see FIG. 8C).

[0108] In this example, the gate voltage is controlled so that thetransistor enters the linear region at a predetermined period at a timeof risingup/decaying-down of the drive current, while it enters the OFFstate during all the other period.

[0109] That is, as shown in FIG. 8B, when the impedance control signalModZ which shows a predetermined period at the rising-up/decaying-downof drive current ILD has a low level, the gate voltage Vctrl is made tobe approximately equal to the power supply voltage Vdd (or Vgs should bebelow the threshold voltage Vth). When the ModZ has a high level, thecontrol is made so that Vctrl<Vo−Vth (Vo is the terminal voltage of theLD). The resistance is gradually controllable by the Vctrl voltage valueat the time the ModZ has the high level. Thereby, the ringing of thelight waveform can be well controlled with a sufficient accuracy evenwith a simple configuration.

[0110] According to the present embodiment, in comparison to theabove-mentioned scheme of controlling the ringing with the snubbercircuit, the light source drive is suitable to be integrated with a CMOSprocess, and also, even when the ringing mode varies due to variation ofthe transmission circuit characteristic or characteristic of the pickupdevice, the ringing otherwise occurring thereby can be well controlledthrough an appropriate setting of the resistance value according to thesecond embodiment of the present invention.

[0111] Thus, by controlling the output impedance of the drive currentoutput part for the predetermined time period near at least one of therising-up and decaying-down of the drive current for the light source,this acts as a dumping resistance component controlling the resonancewhich would otherwise occur due the parasitic inductance occurring inthe wiring to the light source. Accordingly, the ringing or overshootingof the light waveform can be well controlled, and, thus, the light canbe made to occur with a desired waveform. Thereby, when this lightsource is applied to an optical information recording apparatus,accurate record marks can be formed on an optical recording medium.

[0112] Further, as mentioned above, it is possible to achieve theabove-mentioned control of output impendence of the drive current outputpart, by employing the MOS transistor connected in parallel with thedrive current output part which outputs the drive current for the lightsource. In this case, a voltage is applied to the gate of the MOStransistor during a predetermined time period at least one of therising-up and decaying-down of the drive current such that thetransistor then enters the linear region. Thus, the ringing/overshootingof the light waveform can be well controlled with the simpleconfiguration, and a light can be made to be emitted with a desiredlight waveform.

[0113] Furthermore, since the above-mentioned predetermined time can becontrolled, the ringing/overshooting of the light waveform can be wellcontrolled properly according to the wiring to the light source, andthus light can be made to be emitted with a desired light waveform.

[0114] Further, since the above-mentioned output impedance value canthus be controlled, the ringing/overshooting of the light waveform canbe well controlled properly according to the wiring to the light source,and thus light can be made to be emitted with a desired light waveform.

[0115] Next, a third embodiment of the present invention will now bedescribed.

[0116]FIG. 9 shows a block diagram showing a configuration of a lightsource drive according to the third embodiment of the present invention.The light source drive of this embodiment solves the above-mentionedfirst and second problems simultaneously. Since the block of the samereference numeral as that shown in FIG. 3 performs the same operationand function described above, detailed description will be omittedtherefor.

[0117] This light source drive includes the above-mentioned variableresistance part 21 and the above-mentioned resistance setting part 22additionally in the light source drive shown in FIG. 3, as shown. Thus,reduction in the circuit scale is aimed at, using a signal obtained froma logical sum of the superposition signals ModO and ModU as theimpedance control signal for controlling the output impedance of thelight source drive with respect to the LD, in the variable resistancepart 21.

[0118] According to the light source drive of this embodiment, even whena deformation of the light waveform occurs due to a combination of theabove-mentioned first and second problems, the light waveform can bewell shaped according to the combined functions of those of theabove-mentioned first and second embodiments, a light can be made to beemitted with a desired waveform, and exact record marks can be formed.

[0119] Thus, according to the light source drive according to any one ofthe first through third embodiments of the present invention, asuperposition current is provided corresponding to acharging/discharging current needed for a capacitance which occurs inparallel with the light source, during a predetermined time period atrising-up/decaying-down of a drive current of the light source. Thesuperposition current is then added to or subtracted from the drivecurrent appropriately. Furthermore, alternatively or in addition, theoutput impedance of the drive current output part is controlled alsoduring a predetermined time period near the rising-up/decaying-down ofthe drive current. Thereby, a delay/rounding or ringing ofrising-up/decaying-down of the light waveform can be well controlled,and a light can be made to be emitted with a desired light waveform.

[0120] Moreover, the output impedance of the drive current output partmay be controlled according to the superposition signal. Thereby, adelay/rounding or ringing of rising-up/decaying-down of the lightwaveform can be well controlled, and a light can be made to be emittedwith a desired light waveform, even with a simple configuration.

[0121] Accordingly, when this light source drive is applied to anoptical information recording apparatus, formation of exact record markscan be performed.

[0122] Thus, according to the light source drive according to any one ofthe above-mentioned first through third embodiments of the presentinvention, the superposition current generation part generates theovershoot current Ios and undershoot current Ius at the rising-up anddecaying-down timings of the modulation signals Mod1 and Mod2 from themodulation signal generation part. Since they are superposed andsupplied to the drive current of the light source LD, a delay (rounding)of the light waveform otherwise occurring due to the junctioncapacitance of the light source LD etc., can be well controlled, and alight can be made to be emitted with a desired light waveform.

[0123] Next, a fourth embodiment of the present invention will now bedescribed. FIG. 10 is a block diagram showing a configuration of a lightsource drive according to the fourth embodiment of the presentinvention. The same reference numerals are given to the same portionswhich are common in FIGS. 3, 5 and 9, and the duplicated descriptionwill be omitted therefor. The light source drive according to thisfourth embodiment also solves the above-mentioned first problem. Eachsignal of the light source drive of this fourth embodiment will bedescribed also based on FIG. 4.

[0124] Unlike the light source drive part 1 shown in FIG. 3, the lightsource drive part 1 shown in FIG. 10 has the modulation signalgeneration part 4 outside as shown. Moreover, instead of thesuperposition time setting part 15, a superposition time setting part 24is provided in the superposition current generation part 18 of the lightsource drive part 1 shown in FIG. 3. The superposition time control part24 controls the superposition time of the overshoot current Ios and theundershoot current Ius based on a CountEN signal of the control part 17.

[0125] As mentioned above, FIG. 4 shows a case at a time of recording toa phase-change type recording medium. In FIG. 4, a waveform (c) is adesired light waveform, and record marks of (d) are formed fromapplication of this light waveform. Levels Pb, Pe, and Pw of the lightwaveform of (c) are respective beam-application levels of a bottom powerlevel, an erase power level, and a light power level, respectively, andare beam-application levels for which the current ILD′ is set to(Ibias+I0), (Ibias+I0+I1), and (Ibias+I0+I2), respectively. That is, thebeam-application level is determined by the beam-application level dataP0Data, P1Data, and P2Data, which set the current values I0, I1, and I2,respectively.

[0126] The modulation signals Mod1 of (e-1) and Mod2 of (e-2) in FIG. 4are generated corresponding to the record data Wdata of (b) based ondrive waveform information that indicates desired modulation timing ofthe light waveform beforehand set in the modulation signal generationpart 4.

[0127] The superposition signal ModO of (f-1) shown in the figure isgenerated so as to have a light level only during the superposition timeperiods (To1, To2, To3) for the overshoot current according toinstructions coming from the superposition time setting part 24 insynchronization with the rising-up of the modulation signal Mod1 orMod2, in the superposition signal generation part 11. Thereby, theovershoot current Ios is generated and is added to the LD drive current.

[0128] Similarly, the superposition signal ModU of (f-2) shown in thefigure is generated so as to have a high level only during thesuperposition time periods (Tu1) for the undershoot current according toinstructions coming from the superposition time setting part 15synchronized with the decaying-down of the modulation signal Mod2, alsoin the superposition signal generation part 11.

[0129] According to these modulation signals and superposition signals,the current ILD′ of (g) is generated. It is noted that the drive currentILD supplied to the LD is obtained from amplifying the current ILD′.

[0130] That is, the current waveform is obtained superposed with theovershoot current Ios at the time of the rising-up of drive current,while superposed with the undershoot current Ius at the time ofdecaying-down of the same. The current levels 10 through 14 shown in thefigure are current values generated in the current sources 8 and 13,respectively, and the current Ibias corresponds to a threshold currentof the LD provided by the LD control part 7.

[0131] Next, FIG. 11 is a block diagram showing a detailed internalconfiguration of the superposition signal generation part 11, and thesuperposition time control part 24 shown in FIG. 10. Further, FIG. 12shows an example of waveform of each signal shown in FIG. 11.

[0132] As shown in FIG. 11, the superposition signal generation unit 11includes a delay element 57 which has the modulation signal Mod2 inputthereto, and outputs the same signal with a delay time of Δ1 which isdetermined by a value of a current provided thereto, and a logicalcircuit 58 which perform a logical operation of {Mod2&!dMod2}, where‘!dMod2’ means the inverted and delayed signal of Mod2, and outputs theoperation result as the superposition signal ModO. Each signal is shownin FIGS. 12, (a), (b) or (c). The superposition signal generation unit11 also includes a delay element 59 which has the modulation signal Mod2input thereto, and outputs a signal d2Mod2 delayed from the thus-inputsignal Mod2 with a delay time of Δ2, and a logical circuit 60 whichperforms a logical operation of {!Mod2&d2Mod2}, where ‘!Mod2’ means theinverted signal of Mod2, and outputs the operation result as thesuperposition signal ModU.

[0133] The above-mentioned example shows a configuration in which thesuperposition signal ModO is generated in synchronization with therising-up of the modulation signal Mod2. However, it is also possiblethat the superposition signal is generated also at the time of therising-up of the modulation signal Mod1. Moreover, it is possible toconnect a plurality of delay elements in series for the delay element 57or 59.

[0134] The superposition time control part 24 includes delay elements 56a through 56 d each having the same characteristic as each of the delayelements 57 and 59 (that is, the relation of the delay time with respectto the current supplied thereto is common thereamong) which form a ringoscillator 55 (in order to simplify the description, FIG. 11 shows aconfiguration thereof with only four stages of delay elements), acurrent source FqDAC 53 which supplies a current set by an FqData signalto these delay elements 56 a through 56 d, a pulse counter 52 whichmeasures the oscillation frequency of the oscillator 55, a delay timecontrol part 51 which controls the FqData signal so that the oscillationfrequency measured by the pulse counter 52 becomes a predeterminedfrequency, and current sources TODAC 54 a and TuDAC 54 b which supplythe current values set by the delay time control part 51 to the delayelements 57 and 59, respectively.

[0135] In FIG. 12, curves (d-1) through (d-4) show waveforms of theoutput signals of the delay elements 56 a through 56 d, and the curve(d-4) shows the output signal waveform of the oscillator 55.

[0136] The current by which the delay time is set to Δ is supplied toeach of the delay elements 56 a through 56 d, and thus, the oscillationfrequency Fvco of the oscillator 55 is set as 1/(4Δ).

[0137] Therefore, when the output current of the current source FqDAC 53is controlled appropriately so that the oscillation frequency is set toa predetermined 1/(4Δ1), and the same current is made to be suppliedfrom the current source TODAC 54 a, the superposition signal ModO withthe superposition time width of Δ1 can be generated.

[0138] Similarly, when the output current of the current source FqDAC 53is controlled appropriately so that the oscillation frequency is set toa predetermined 1/(4Δ2), and the same current is made to be suppliedfrom the current source TODAC 54 b, the superposition signal ModU withthe superposition time width of Δ2 can be generated.

[0139] Next, control processing for the above-mentioned delay time,i.e., control processing for the oscillation frequency will now bedescribed. The oscillator 55 is an oscillator which has the frequencysetting current Ivco provided thereto which the current source FqDAC 53outputs, and is thus made to generate the signal of frequency Fvco. Thisfunction is the same as that of a well-known VCO (Voltage ControlledOscillator).

[0140]FIG. 13 shows an example of a characteristic of the oscillationfrequency Fvco with respect to the above-mentioned frequency settingcurrent Ivco. According to a variation in devices etc., thecharacteristic varies in a usual VCO, as shown in curves (a) and (b) inFIG. 13. That is, even when a predetermined frequency setting currentIvco is provided, a desired frequency Ftarget may not be obtained veryaccurately. However, according to the light source drive in the fourthembodiment of the present invention described above, it is controllableby the control processing described below into a desired frequencyFtarget very accurately with a simple scheme.

[0141] The pulse counter 52 counts the number of output pulses of theoscillator 55 during a predetermined frequency measurement time Tcountindicated by the CountEN signal supplied from the control part 17 (thepulse measurement result therefrom is assumed as a VCOCount). Therefrom,the oscillation frequency Fvco of the oscillator 55 is detectable withoperation processing based on a formula (1).

Fvco=VCOCount/Tcount  (1)

[0142] The delay time control part 51 performs a control such as tochange the data FqData to be set to the current source FqDAC 53 so thatit may become the predetermined value Ftarget based on the pulsemeasurement result VCOCount.

[0143] The delay time control part 51 may be provided, for example, inthe controller 19. In this case, transfer of the pulse measurementresult VCOCount and Data FqData should be made via the control part 17.

[0144]FIG. 14 shows signal waveforms for illustrating the processing ofmeasuring the above-mentioned oscillation frequency, and shows signalsof essential parts shown in FIGS. 10 and 11.

[0145] Each signal of (a) SEN, (b) SCK, and (c) SDIO shown performscommunications between the controller 19 and the control part 17. The(a) SEN indicates an enable state of communications, the (b) SCKperforms clock supply, and the (c) SDIO indicates address data. Theclock frequency of SCK of (b) is supplied with a predetermined frequencyfsck (the period is set to Tsck).

[0146] The signal SDIO of (c) is sent/received in synchronization withthe SCK signal. The former 8 bits of this signal SDIO indicates anaddress (the first 1 bit thereof indicates read/write), while the latter8 bits thereof indicates data to be communicated. In case theoscillation frequency in the VCO is measured, a write access to apredetermined address (HFCheck) is performed, the control part 17responds thereto so as to indicates the period (for which the data istransferred) by causing the signal CountEN to have a high level as shownin FIG. 14, (d). In response thereto, the pulse counter 52 counts thepulses of the output of the VCO (oscillator output) shown in FIG. 14,(e) during this period (FIG. 14, (f) shows the count value VCOCount).During the period in which the signal CountEN shown in FIG. 14, (d) hasa low level, no such a counting is performed, and the count value isthen held. Thereby, the measurement of the frequency of the output ofthe oscillator 55 (VCO) is made positively, is utilized for theabove-mentioned control such that the frequency is controlled into thetarget value.

[0147] Thereby, even when the characteristic of the oscillationfrequency Fvco with respect to the frequency setting current Ivco of theVCO varies as shown in FIGS. 13, (a) and (b), due to a variation indevice product, etc., it becomes possible to achieve a control with thevery simple configuration to obtain the desired oscillation frequencyFtarget at high accuracy.

[0148] Therefore, the superposition signal ModO produced using the delayelements with the same characteristic as in the oscillator 55 can becontrolled at the desired superposition time Δ1 accurately. A similarcontrol should then be performed so that the desired superposition timeΔ2 is obtained accurately.

[0149] Such a time control may be performed always, or may be performedonly when the machine is started up, or in another appropriate timing.

[0150] The overshoot current Ios and the undershoot current Ius thusgenerated and superposed are used as charging/discharging currents forthe junction capacitance of the LD. Accordingly, a delay of therising-up/decaying-down timing or rounding of the light waveform can beavoided. Accordingly, a light can be made to be emitted with a desiredlight waveform from the LD, and thus, exact record marks can be formedon the optical recording medium.

[0151] Further, even when a variation occurs in particular deviceproduct, appropriate control can be achieved without increasing thenumber of signal wires used for signal transmission. Accordingly, thepresent invention in this embodiment is advantageous forminiaturizing/price reduction of the apparatus.

[0152] Further, according to the present invention, as shown in FIG. 10,the superposition signal generation part 11 is provided in common withinthe IC chip of the LD driver 1. Accordingly, it is not necessary toprovided external wiring between the superposition signal generationpart 11 and the LD driver 1, also, extra external terminal contactstherefor are not needed in this IC chip. Thus, miniaturization and costreduction in the apparatus may be archived effectively.

[0153] The above-mentioned junction capacitance may differ according toa particular product of the LD applied. Accordingly, it is preferablethat the above-mentioned superposition current values should bepreferably adjusted accordingly. Thereby, appropriatecharging/discharging of the junction capacitance of the LD can beachieved, thus, a still more ideal light waveform can be provided, and amore excellent record mark formation can be performed. In the lightsource drive according to the fourth embodiment of the presentinvention, the superposition current value setting part 16 executes thisfunction. The same effect is acquired by adjusting the superpositiontime of overshoot current Ios and undershoot current Ius, instead. Inthe light source drive of the fourth embodiment, the superposition timesetting part 15 executes this function. It is also possible to combinethese functions.

[0154] Furthermore, it is further preferable to adjust the currentvalues and/or the superposition times of the overshoot current Ios andthe undershoot current Ius according to change in the beam-applicationlevels. That is, according to changes in the beam-application level,i.e., Pe→Pw, Pb→Pw, Pb→Pe), the amount of change in the potential acrossthe cathode and anode of the LD differs, and thus, thecharging/discharging current needed changes accordingly. Therefore, whenthe superposition times (To1, To2, To3) are controlled according to thethus changing beam-application level shift, the rising-up/delaying-downtiming or rounding of the light waveform can be controlled more finely.The same effect can be acquired by controlling the current values.

[0155] Moreover, by configuring such that the pulse count resultVCOCount shown in FIG. 11 is held at the maximum value in case the pulsecounter overflows, an erroneous control can be avoided. Furthermore, aconfiguration may be made such that the pulse counter 52 shown in FIG.11 measures an 1/N frequency divided signal of the oscillator output.Thereby, the pulse counter should not be operated at high speed.

[0156] The form of communications made between the controller 19 and thecontrol part 17 described above with reference to FIGS. 10 and 14 ismerely one example. Even when another form of communications is applied,it is possible to achieve a similarly measurement by using the transferclock signal.

[0157] Moreover, it is also possible instead that the signal of CountENis produced shown in FIG. 14, (g) instead of that shown in FIG. 14, (d),and the counting is performed through a normal accessing occasion. Then,upon a write access to the predetermined address (HFCheck) is made, theVCO pulse measurement result of VCOCount shown in FIG. 14, (i) may beheld. Thereby, it becomes possible to elongate the measurement timeperiod Tcount, and, thus, it becomes possible to achieve more preciseoscillation frequency detection.

[0158] Alternatively, it is also possible that the CountEN signal shownin FIG. 14, (g) is produced for an access which is made subsequently tothe write access to the predetermined address (HFCheck).

[0159] Moreover, an SCK frequency setting part which sets the frequencyof the SCK signal may be provided in the controller 19, and, thereby,the frequency of the SCK signal may be changed so that the frequencymeasurement time Tcount may be changed accordingly, appropriately.

[0160] Thereby, it becomes possible to elongate the measurement timeTcount within a range in which the pulse counter 52 does not overflow.Accordingly, it becomes possible to increase the accuracy of themeasurement effectively.

[0161] Then, during a normal communication occasion, the SCK clockfrequency may be made higher so that high-rate transfer is achieved,while, at a time of the superposition frequency measurement, the SCKclock frequency may be lowered so that the accuracy of the measurementis improved.

[0162] In addition, in order to reduce LD noise by a reflected lightfrom a disk to the optical disk drive, usually, a method, called ‘highfrequency superposition’, of superposing a high frequency signal on adrive current for the LD may be taken in some cases. In such a case,since it is a common way to use an oscillator (VCO), and, therefore,this oscillator may be used in common also as the above-mentionedoscillator 55.

[0163]FIG. 15 shows a block diagram showing a configuration of a lightsource drive according to a fifth embodiment of the present invention.The light source drive of this embodiment solves the above-mentionedsecond problem. Each block having the same reference numeral as thatshown in FIGS. 3, 5, 9 and 10 performs the same operation and functionas described, and, thus detailed description thereof will be omittedtherefor.

[0164] As shown in FIG. 15, in parallel with a current source whichprovides the output current of the current drive part 6, a variableresistance part 73 is connected which controls the output impedance ofthe light source drive part 1. According to an impedance control signalModZ, this variable resistance part 73 has a resistance Rd according toa resistance value setting signal Svr when the ModZ=High (high level),while this has an approximately infinite resistance when the ModZ=Low(low level).

[0165] A resistance setting part 74 generates the resistance settingsignal Svr which indicates a resistance for a case where the lowerimpedance is provided by the variable resistance part 73 as mentionedabove.

[0166] An impedance control signal generation part 72 starts up insynchronization with the modulation timing (which corresponds to therising-up or decaying-down timing of the modulation signals Mod1 andMod2, or a part thereof) supplied from the modulation signal generationpart 4, and generates the impedance control signal ModZ having a highlevel only during a period set by a dumping time setting part 71. Theseparts 71 through 74 execute a function of controlling the outputimpedance.

[0167]FIG. 16 shows a circuit diagram for illustrating control operationof a function of controlling a ringing of a light waveform occurring dueto a parasitic inductance, which is the above-mentioned second problem.

[0168] A ringing of the light waveform occurs due to a resonanceoccurring in a loop indicated by a broken arrow shown in FIG. 16. Whatis necessary is just to connect a resistance component to this loop inparallel, in order to control this resonance. The resistance componentshould just be connected at a time of the rising-up/decaying-down of thedrive current at which ringing would otherwise occur. The current source80 shown in FIG. 16 corresponds to a current source at an output stagewhich supplies an output current of the current drive part 6 shown inFIG. 15.

[0169] A variable resistance part 81 shown in FIG. 16 achieves thisfunction, and the variable resistance part 73 shown in FIG. 15corresponds thereto. This includes a switch 83 and a resistor 84, andon-off control is carried out by the switch according to the impedancecontrol signal ModZ. In case the resistor 84 is made of a variableresistor for which the resistance thereof is set by the resistancesetting signal Svr, and the resistance is set according to thetransmission circuit characteristic between the light source drive part1 and the LD, ringing can be controlled more appropriately and a lightcan be made to be emitted by the LD with a desired light waveform.

[0170] Moreover, as the power supply VDD and the ground areshort-circuited in terms of AC operation, the variable resistance part82 may be connected as shown in FIG. 16.

[0171]FIG. 17 shows another example of the variable resistance part 73shown in FIG. 15. This variable resistance part has a parallelconnection of resistors R1 through Rn with switches SW1 through SWnconnected in series, respectively. One of the switch is selectedaccording to the resistance setting signal Svr, while an on-off controlis performed on the thus-selected switch according to the impedancecontrol signal ModZ. According to the thus-configured variableresistance part, it becomes possible to effectively control ringing inresponse to the transmission circuit characteristic with a simpleconfiguration.

[0172] Although not shown, details of the impendence control signalgeneration part 72 and dumping time control part 71 may be the same asthose shown in FIG. 11.

[0173] According to the present embodiment, in comparison to theabove-mentioned scheme of controlling ringing with the snubber circuitin the related art, the light source drive is suitable to be integratedwith a CMOS process, and also, even when a ringing mode varies due to avariation of the transmission circuit characteristic or characteristicof the pickup device, the ringing otherwise occurring thereby can bewell controlled through an appropriate setting of the resistance value.

[0174] Further, the time interval during which the dumpling resistanceshould be switched on can be set properly. Furthermore, even when thedevices have variations, a proper control can be achieved. Also, asimple configuration can do well, and the proper control is achievedwithout increase of the number of transmission lines. Accordingly, thepresent embodiment is advantageous for miniaturizing/cost reduction ofthe light-source drive.

[0175] Next, a sixth embodiment of the present invention will now bedescribed. FIG. 18 is a block diagram showing a configuration of a lightsource drive according to the sixth embodiment of the present invention.The same reference numerals are given to parts same as those shown inFIGS. 3, 5, 9, 10 and 15, and duplicated descriptions will be omitted.The light source drive according to the sixth embodiment solves theabove-mentioned first and the second problems.

[0176] As shown in FIG. 18, a shaping signal generation part 91 and ashaping time control part 92 generate the superposition signals ModO andModU and the impedance control signal ModZ as in the above-mentionedembodiments. A detailed configuration thereof may be same as that shownin FIG. 11.

[0177] According to the light source drive in this sixth embodiment, itis possible to shape a light waveform of laser beam so as to cope with adeformation in waveform which would otherwise occur due to a cause incombination of the above-mentioned first and second problems. Thereby, alight beam can be made to be emitted by the LD with a desired waveform,and formation of an exact record mark can be archived on the opticaldisk.

[0178] Thus, according to the above-mentioned fourth through sixthembodiments of the present invention, a deformation of light waveformresulting from parasitic devices such as capacitances, inductances or soproduced in transmission wires installed toward the light source or thelight source itself can be corrected. Accordingly, a deformation inwaveform of light beam (such as a delay or rounding in arising-up/decaying-down, or ringing) can be well reduced, and, thus,light beam emission can be performed with a desired waveform.

[0179] Furthermore, as superposition current is produced and isappropriated as a current necessary for charging/discharging a junctioncapacitance or so of the light source, a delay or rounding ofrising-up/decaying-down in the light waveform occurring due to thecapacitance can be well reduced. Thus, light beam emission can beperformed with a desired waveform.

[0180] Furthermore, as the superposition current can be applied at aproper timing, a possible excessive overshooting can also be positivelyavoided.

[0181] Furthermore, as the output impedance of the drive current outputcan be controlled during a period near at least one of a rising-up and adecaying-down of the drive current for the light source, this functionsto well control a resonance otherwise occurring due to the parasiticimpedance or so occurring in the transmission wires installed toward thelight source, and, thus, well control ring/overshooting in the lightwaveform so that the light beam is emitted with a desired waveform.

[0182] Furthermore, a delay or rounding of rising-up/decaying-down oflight waveform, or ringing can be well controlled, and a light beam(laser beam) can be emitted with a desired waveform.

[0183] Furthermore, a timing at which a waveform shaping should beperformed can be properly determined.

[0184] Furthermore, as the time period for which the frequency detectionis performed can be elongated as mentioned above, the frequencydetection can be achieved with a high accuracy, and, thereby, asmentioned above, the waveform shaping can be performed more accurately.

[0185] Furthermore, when any of the present embodiments of the presentinvention is applied to an optical information recording apparatus, anaccurate record mark can be formed on an optical recording medium suchas an optical disk. Further, even there are variations in performance ofdevice products employed in the apparatus, a proper and simpleconfiguration can achieve an excellent control of light waveform,without increase in the number of transmission wires. Accordingly, theapparatus can be effectively miniaturized or reduced in the costs.

[0186] A seventh embodiment of the present invention will now bedescribed.

[0187] As described above, in a pigment-system write-once-type opticaldisk such as a CD-R, DVD+R disk, or so, a record mark is formed byproducing an optical change by a thermal decomposition thanks to a lightbeam application or to a substrate deformation occurring therewith.Therefore, in order to form a proper mark shape or to control a markformation position accurately, a proper light waveform should beproduced. A similar situation occurs also on a magneto-optical recordingmedium such as an MO, MD or so, in which magnetism inversion near theCurie point is utilized.

[0188] Specifically, in each of these recording media, the recordingmedium is increased in temperature by application of a laser beam to arecording layer thereof, whereby physical or chemical transformationoccurs there and thus optical recording is achieved. Accordingly, it isimportant to properly control a beam application energy applied onto therecording medium, i.e., a beam application power and a beam applicationtime duration.

[0189] In recording methods for various types of optical disks, such asa CD, a DVD, and so forth, a mark edge recording method which issuitable for high-density recording, is employed, in which informationis recorded according to a mark length formed. In this method, tocontrol a mark shape and to control an edge position of the mark isessential.

[0190] Further, as it is necessary to well control a mark shapeuniformly among various mark lengths, a multi-pulse recording method iswidely employed in which a plurality of separate recording pulses areused for forming a long mark.

[0191] Specifically, a uniform long mark is formed by repeating a cycleof heating and cooling, and connecting respective marks formed therefrominto the continuous long mark. Such a recording method is applied alsofor the above-mentioned pigment-system write-once-type recording medium.Hereinafter, a pulse used for an application of a laser beam with a highpower so as to increase the recording medium in temperature will bereferred to as a heating pulse, while a pulse for an application of alaser beam with a low power so as to prevent the recording medium frombeing increased in temperature or to rapidly cool the same will bereferred to as a cooling pulse.

[0192] For the above-mentioned reason, conventionally, the time-axisresolution should be increased in an application of laser beam so as toperform the mark positional control for high-speed recording. Forexample, Japanese laid-open patent application No. 8-287465 discloses amethod for appropriately correcting an application time duration as wellas a cooling time duration because both an accuracy of a beamapplication energy and an accuracy of a cooling time are importantespecially for a phase-change recording medium in an optical informationrecording apparatus.

[0193] High-speed optical modulation is demanded for high-speed opticalrecording recently. In order to increase the rate at which informationis recorded while the recording quality is maintained, it is necessaryto increase the time-axis resolution of application time and coolingtime for laser beam application onto the optical disk. For example,conventionally, for achieving ten-time recording of DVD, a time-axisresolution as high as approximately 100 ps is needed.

[0194] However, according to a conventional optical informationrecording apparatus, there is a problem of difficulty in achieving sucha high-speed recording, or needing a considerable cost rise.

[0195] Moreover, as will be described, proper heating and cooling maynot be achieved, as a delay or rounding of a rising-up/decaying-down oflight waveform occurs together with increase in the recording speed.Thereby, the mark shape or mark position may not be controlled at highaccuracy.

[0196]FIG. 19 shows a circuit diagram of a configuration for driving anLD (laser diode) in a light source driver for the purpose ofillustrating the above-mentioned problem. It is noted that an LD drivepart 1201 omits illustration except a current source which supplies adrive current. Moreover, FIG. 20 shows light waveforms in an example oflaser beam emitted from the LD by the circuit shown in FIG. 19.

[0197] The LD usually has a junction capacitance between the anode andcathode (in addition, parasitic capacitance also may occur there). Thecircuit shown in FIG. 19 includes a simple LD equivalent model 1202 inconsideration of this junction capacitance. As shown, this equivalentmodel includes the junction capacitance CLD also including the parasiticcapacitance, an turned-on resistance ‘r’ and an ideal LD ‘LDi’.

[0198] Due to this junction capacitance, even when a predetermined drivecurrent ILD with a sharp rising-up and a sharp decaying-down as shown inFIG. 20, (a), is applied, an actual current flowing through the idealLD, LDi has a delay or rounding of the rising-up/decaying-down as shownin FIG. 20, (b). This is because a partial current Ic is consumed forcharging/discharging the junction capacitance CLD, and, thus, thecurrent to actually flow through the ideal LD, LDi is changed during thecharging/discharging operation. As a result, the delay occurs in therising-up/decaying-down in the waveform as shown in FIG. 20, (b). As aresult, the LD emits a laser beam with a waveform shown in the solidcurve of FIG. 20, (b), which is different and deteriorated from thedesired waveform indicated by the broken curve in the same figure.

[0199] When the accuracy in mark shape or mark position is thusdegraded, data error may occur accordingly in information recording ontothe optical disk. Especially, an LD with a high power is needed forachieving high-speed recording, such an LD having a high power has alarge junction capacitance accordingly in general, and, also, ahigh-speed or sharp rising-up/decaying-down is needed. In such a case,this type of problem becomes remarkably worse accordingly.

[0200] The seventh embodiment of the present invention solves thisproblem, and aims at forming an exact record mark without actuallyimproving the time-axis resolution for beam-application time and coolingtime also in the case of performing high-speed recording. Moreover, asin the above-mentioned embodiments of the present invention, the seventhembodiment also has a purpose to control or well reduce a delay orrounding of rising-up/decaying-down in a light waveform which wouldotherwise occur due to the junction capacitance of the LD, etc., so asto enable beam emission with a desired waveform whereby a record mark isformed properly at high accuracy.

[0201]FIG. 21 shows a block diagram of a main configuration of anoptical information recording apparatus in the seventh embodiment of thepresent invention. FIG. 22 shows waveforms of signals of respectiveparts of the optical information recording apparatus shown in FIG. 21.This optical information recording apparatus is an optical disk drive,such as a CD-R drive, a CD-RW drive, a DVD-R drive, a DVD-RW drive, aDVD+RW drive, a DVD-RAM drive, or so.

[0202] In FIG. 21, a light source drive part 101 includes abeam-application level setting part 102 which outputs respective data,i.e., P0Data, P1Data and P2Data, which sets beam-application levels ofan LD, i.e., P0, P1, and P2. A modification signal generation part 104also included in the light source drive 101 generates and outputsmodification signals Mod1 and Mod2 for the LD from a record data signalWdata and a record clock signal WCK.

[0203] A modification part 103 also included in the light source drive101 generates and outputs an LD modification current Imod based on thebeam-application level data P0Data, P1Data and P2Data corresponding tothe respective beam-application levels of P0, P1, and P2 of the LD andthe modification signals Mod1 and Mod2. An addition current generationpart 118 also included in the light source drive 101 generates anovershoot current Ios and an undershoot current Ius which superpose anaddition power to the heating pulse and an addition power to the coolingpulse, respectively (referred to as addition currents Ios and Ius,respectively, hereinafter), based on modulation timings (whichcorrespond to rising-up or decaying-down timings of the modulationsignals Mod1 and Mod2, or to their parts) which the modulation signalgeneration part 104 generates.

[0204] An LD control part 107 controls a bias current Ibias and a scalesignal Iscl which indicates a scale of a modulation current so that alight emission amount of the LD becomes a desired value based on amonitor light-receiving signal, which is input from a monitoring PDwhich monitors a part of the emitted light of the LD.

[0205] An addition-and-subtraction part 105 adds the LD modulationcurrent Imod and the bias current Ibias together, further adds theretothe overshoot current Ios, or subtracts the undershoot current Iustherefrom. A current drive part 106 amplifies a current ILD′ provided bythe addition-and-subtraction part 105 and provides a drive current ILDto the LD. A control part 117 receives control commands provided by acontroller 119 which controls the entirety of an information recordingapparatus which includes the above-mentioned light source drive 101, andprovides control signals to the respective parts.

[0206] Next, a detailed internal configuration of the modulation part103 will now be described. The modulation part 103 includes a currentsource 108 which supplies currents I0, I1, and I2 based on thebeam-application level data P0Data, P1Data, and P2Data, respectively,which source actually includes respective current sources P0DAC 108 a,P1DAC 108 b, and P2DAC 108 c. Switches 109 b and 109 c carry out on-offcontrol of the currents I1 and I2 according to the modulation signalsMod1 and Mod2, respectively, and an addition part 110 which adds eachcurrent together which the switches 109 output while they are turned on,and supplies an LD modulation current Imod.

[0207] Next, a detailed internal configuration of the addition currentgeneration part 118 will now be described. The addition currentgeneration part 118 includes an addition signal generation part 111which generates addition signals (respectively, ModO and ModU) whichspecify periods for which the overshoot current Ios and undershootcurrent Ius are superposed based on the modulation timings which themodulation signal generation part 104 generates. An addition powersetting part 116 sets current values I3 and I4 of the overshoot currentIos and undershoot current Ius, and supplies setting data OSData andUSData therefor.

[0208] Current sources OSDAC 113 a and USDAC 113 b supply the currentsI3 and I4 based on the overshoot current setting data OSData and theundershoot current setting data USData, respectively. Switches 114 a and114 b carry out on-off control of the currents 13 and 14 according tothe addition signals ModO and ModU, respectively, and thus generate theovershoot current Ios and undershoot current Ius. An addition timesetting part 115 sets addition time periods for the overshoot currentIos and undershoot current Ius.

[0209] The LD control part 107 may be configured by utilization of awell-known art, and a description of the details thereof will beomitted. The above-mentioned scale signal Iscl should be controlledaccording to the differential quantum efficiency of the LD so that thebias current Ibias becomes approximately equal to the threshold currentIth.

[0210]FIG. 22 shows the waveform showing an example of a main signal ofeach part shown in FIG. 21. This figure shows a case at a time ofrecording to a phase-change type recording medium. In FIG. 22, awaveform (c) is a desired light waveform, and record marks of (d) areformed from application of this light waveform. Levels Pb, Pe, and Pw ofthe light waveform of (c) are respective beam-application levels of abottom power level, an erase power level, and a light power level,respectively, and are beam-application levels for which the current ILD′is set to (Ibias+I0), (Ibias+I0+I1), and (Ibias+I0+I2), respectively, asshown. That is, the beam-application levels are determined by thebeam-application level data P0Data, P1Data, and P2Data, which set thecurrent values I0, I1, and I2, respectively.

[0211] In FIG. 22, a power level Pw2 is a beam-application levelobtained from addition of a certain power to the above-mentioned writepower level Pw, and the certain power added (Pw2−Pw) corresponds to theabove-mentioned current 13. Similarly, a power level Pb2 is abeam-application level obtained from subtraction of a certain power fromthe above-mentioned bottom power level Pb, which certain powersubtracted corresponds to the above-mentioned current 14.

[0212] Then, as shown in FIG. 22, (d), a front edge part ‘a’ of a recordmark is formed with a top pulse TP, shown in FIG. 22, (c), and a coolingpulse subsequent thereto; a rear edge part ‘c’ of the record mark isformed with a last pulse LP and a cooling pulse subsequent thereto; andintermediate parts ‘b1’ and ‘b2’ of the record mark are formed withintermediate pulses MP and cooling pulses subsequent thereto,respectively. Thus, the one record mark corresponding to the record dataWdata shown in FIG. 22, (b) is formed.

[0213] The modulation signals Mod1 of (e-1) and Mod2 of (e-2) in FIG. 22are generated corresponding to the record data Wdata of (b) based ondrive waveform information that indicates desired modulation timing ofthe light waveform beforehand set in the modulation signal generationpart 104.

[0214] The addition signal ModO of (f-1) shown in the figure isgenerated so as to have a high level only during the addition timeperiods (To1, To2, To3) for the overshoot current according toinstructions coming from the addition time setting part 115 insynchronization with the rising-up of the modulation signal Mod1 or Mod2in the addition signal generation part 111. These addition time periodsTo1, To2 and To3 indicate the addition time periods for theabove-mentioned pulses TP, MP and LP. Thereby, the overshoot current Iosis generated and is added to the LD drive current.

[0215] Similarly, the addition signal ModU of (f-2) shown in FIG. 22 isgenerated so as to have a high level only during addition time periods(Tu1, Tu2, Tu3) for the undershoot current according to instructionscoming from the addition time setting part 115 synchronized with thedecaying-down of the modulation signal Mod2. According to thesemodulation signals and addition signals, the drive current ILD isproduced, and, according thereto, the light waveform shown in FIG. 22,(c) is obtained.

[0216] In other words, the addition power is added at a time of eachrising-up of heating pulse, while the addition power is subtracted at atime of each decaying-down of the heating pulse (or at the top of eachcooling pulse).

[0217]FIG. 23 shows a relation between the heating pulse having theabove-mentioned addition power added thereto, and the beam-applicationenergy applied thereby to the optical recording medium. In this figure,a light waveform (a) is a waveform obtained when an addition power ΔP isnot added, and light waveforms (b) through (e) are waveforms obtainedwhen the addition power is added one by one, respectively.

[0218] Since the beam-application energy is obtained from integration ofthe beam-application power, the beam-application energies correspondingto the respective light waveforms (a) through (e) are those shown inFIG. 23. Light waveforms (c′) and (e′) shown are those for which thebeam-application power is controlled not by addition of the additionpower but by elongating the heating pulse width. These waveforms (c′)and (e′) have the beam-application energies same as those of thewaveforms (c) and (e), respectively.

[0219] As mentioned above, formation of a record mark is achieved fromheating of the recording material of the recording medium. There, byimproving the resolution of the beam-application energy applied to therecording material, a thermal transformation of the recording medium canbe controlled at high accuracy. Thereby, high-accuracy mark formationcontrol is achieved.

[0220] Thus, according to the seventh embodiment of the presentinvention described above with reference to FIGS. 21, 22 and 23, theresolution of the beam-application energy is increased by controllingthe pulse width of the addition power which is added to the heatingpulse, without increasing the time-axis resolution of the heating pulseitself. Thereby, it becomes possible to achieve high-accuracy markformation control easily. This scheme is advantageous especially in acase of high-speed recording where further improvement of pulse widthresolution is difficult. In fact as shown in FIG. 23, finer control ofbeam-application energy can be achieved by controlling the pulse widthof the addition power than by controlling the pulse width of the heatingpulse itself. That is, the beam-application energy control can be madetwice, i.e., in possible steps of (c), (d) and (e) by utilization of theaddition power than merely in possible steps of (c′) and (e′) only withthe conventional pulse width control of heating pulse, with the samepulse width resolution.

[0221] Similarly, as to the cooling pulse, by subtracting the additionpower therefrom, it becomes possible to finely control the coolingspeed, and, thus, more accurate mark formation control is attained.

[0222] Moreover, by adjusting the addition signal pulse widths (To1,To2, To3, and Tu1, Tu2, Tu3) for which the addition powers are added toor subtracted from the top pulse TP, the intermediate pulses MP, and thelast pulse LP, respectively, the form of the front edge part, theintermediate parts, and the rear edge part of the record mark can beshaped with sufficient accuracy, and thus an accurate record mark can beformed uniformly.

[0223] In some type of optical recording medium, as it has a high heatconductivity, a formation of a record mark may be influenced by adjacentrecord marks, and thereby, an edge shift phenomenon may occur, due to aheat storage effect. In particular, in a pigment-system write-once-typerecording medium, this tendency is remarkable in general. For solvingthis problem, conventionally, the pulse width of a recording pulse iscontrolled according to the lengths of spaces occurring before and aftera relevant record mark. However, as in the same reason as that mentionedabove, in case of high-speed recording, it is difficult to finelycontrol the time-axis resolution for the purpose of the above-mentionedcontrol in response to the lengths of spaces before and after therelevant record mark.

[0224] A first variant embodiment of the above-mentioned seventhembodiment of the present invention will now be described which cansolve this problem. Description duplicate with that made for the seventhembodiment will be omitted.

[0225] According to the first variant embodiment of the seventhembodiment, the modification signal generation part 104 shown in FIG. 22measures the run length of the record data Wdata input, and suppliesinformation concerning a mark length M1, an immediately preceding spacelength S0, and an immediately subsequent space length S1, to theaddition time setting part 115. Simultaneously, the modification signalsMod1 and Mod2 are also generated based on these lengths M1, S0, and S1.

[0226] The addition time setting part 115 determines the addition times(To1, To2, To3, and Tu1, Tu2, Tu3) according to the lengths M1, S0, andS1 which are supplied thereto, and supplies thus-determined time data tothe addition signal generation part 111.

[0227] Thereby, the beam-application energy can be adjusted inconsideration of the heat transferred from the adjusted record marks,and, thus, a highly precisely controlled record mark can be formed.

[0228] In addition, reduction in the circuit size can also be attainedwhile the above-mentioned advantage is maintained, when the informationof run-length which has a higher influence is particularly used forcorrecting each addition time accordingly.

[0229] Specifically, the addition times To1 and Tu1 may be determinedfor the top pulse TP according to the immediately preceding space S0 andthe mark length M1, while the addition times To3 and Tu3 may bedetermined for the last pulse LP according to the mark length M1 and theimmediately subsequent space length S1. Furthermore, the addition timesTo2 and Tu2 may be determined for the intermediate pulses MP accordingto the mark length M1. Thereby, the effectively simplified control ofbeam-application energy is achieved.

[0230] Next, a second variant embodiment of the seventh embodiment ofthe present invention will now be described. This second variantembodiment of the seventh embodiment is advantageous in use of an LDwhich has a delay or rounding in rising-up/decaying-down of a lightwaveform thereof due to the influence of the junction capacitance of theLD such as that mentioned above.

[0231] According to an information recording apparatus according to thesecond variant embodiment of the seventh embodiment, what is differentfrom the above-mentioned seventh embodiment is that the addition timedetermined by the above-mentioned addition time setting part 115 isincreased by an amount approximately corresponding to acharging/discharging time needed for the junction capacitance of the LD.Assuming that the time period to be added to the addition time is Δt, Δtis determined such that Δt·I3 corresponds to the charging current neededfor the junction capacitance.

[0232]FIG. 24 shows waveforms of a drive current for the LD and a lightwaveform, used for illustrating operation of this second variantembodiment of the seventh embodiment.

[0233] In FIG. 24, (i), the waveform ‘a’ of the drive current ILD forthe LD is one in a case where the above-mentioned overshoot current Iosis not added on a rising-up of the drive current. Waveforms ‘b’ through‘d’ are those in case where the predetermined addition time of overshootcurrent Ios is added one by one gradually. In FIG. 24, (ii), a lightwaveform is shown as an example resulting from each of theabove-mentioned drive currents ILD shown in FIG. 24, (i). As for thelight waveform ‘a’, a rising-up is remarkably rounded due to the currentconsumed to charge the junction capacitance of the LD, and the lightwaveform ‘b’ results from a case where the added overshoot current Iosis exactly appropriated for the necessary charging current. The lightwaveforms ‘c’ and ‘d’ are those resulting from a case where the timeadded is further increased, and, thus, as in the above-mentioned seventhembodiment, the resolution of beam-application energy is increasedaccordingly.

[0234] As parts of the thus-generated overshoot current Ios andundershoot current Ius are used as the charging/discharging currents forthe junction current of the LD to drive, it becomes possible to wellreduce a delay in time or rounding of rising-up/decaying-down of lightwaveform effectively. Furthermore, the remaining ones of the appliedcurrent are used for adding or subtracting the addition power to/fromthe heating power, and, thereby, it becomes possible to improve theresolution of beam-application energy applied. As a result, a light canbe made to be emitted with a desired light waveform, and exact recordmark formation can be performed.

[0235] The junction capacitance may differ according to a particularproduct of the LD applied. Accordingly, it is preferable that theabove-mentioned addition current values should be adjusted accordingly.Thereby, appropriate charging/discharging of the junction capacitance ofthe LD can be achieved, thus, a still more ideal light waveform can beprovided, and a more excellent record mark formation can be performed.In the light source drive according to the seventh embodiment andvariant embodiments thereof of the present invention, the additioncurrent value setting part 116 executes this function.

[0236] Furthermore, the same effect is acquired by adjusting theaddition times of overshoot current Ios and undershoot current Ius,instead. In the light source drive of the seventh embodiment and variantembodiments thereof, the addition time setting part 115 executes thisfunction.

[0237] It is also possible to combine these functions.

[0238] Furthermore, it is further preferable to adjust the currentvalues and/or the addition times of the overshoot current Ios and theundershoot current Ius according to various changes of beam-applicationlevels.

[0239] Specifically, according to variation in the beam-applicationlevel, i.e., Pe→Pw, Pb→Pw, Pb→Pe), the amounts of change in thepotential across the cathode and anode of the relevant LD differ, andthus, the charging/discharging current needed changes accordingly. Then,by controlling the addition times (To1, To2, To3; or Tu1, Tu2, Tu3)according to the thus varying beam-application level shift, therising-up/delaying-down timing or rounding of the light waveform can becontrolled more finely. The same effect can be acquired by controllingthe current values.

[0240] Thus, according to the seventh embodiment and variant embodimentsof the present invention, for a predetermined time period, an additionpulse of predetermined power is added near a rising-up of at least somepulses of a pulse series, and the width of the added pulse is adjusted.Accordingly, without improving the resolution of pulse width, theresolution of beam-application energy can be improved easily andaccurate mark formation control is attained. This scheme is advantageousfor a case of high-speed recording where further improving of the pulsewidth resolution is difficult.

[0241] Furthermore, according to the seventh embodiment and variantembodiments of the present invention, for a predetermined time period, afirst addition pulse of predetermined power is added near a rising-up ofat least some pulses of a pulse series, and the width of the added pulseis adjusted as mentioned above. Further, in addition, for apredetermined time period, a second addition pulse of predeterminedpower is added near a decaying-down of at least some pulses of the pulseseries, and the width of the added pulse is also adjusted. Accordingly,without improving the resolution of pulse width, the resolution ofbeam-application energy can be improved and accurate mark formationcontrol is attained. Also, the cooling speed for cooling the recordingmedium after heating the same by the heating pulse can be further finelycontrolled. Accordingly, it becomes possible to more positively achieveaccurate control record mark formation.

[0242] Furthermore, according to the seventh embodiment and variantembodiments of the present invention, a predetermined addition currentis added/subtracted to/from a drive current after and nearrising-up/decaying-down of at least part of a pulse series, and a partof thus-added current is made to be used for charging/discharging forthe junction capacitance of the LD to drive, while the remainingcurrents are used for further shaping the light waveform.

[0243] Furthermore, a predetermined time for which the addition currentis added is controlled. Accordingly, a delay in time/rounding ofrising-up/decaying-down of light waveform otherwise occurring due to thejunction capacitance of the LD or so can be effectively controlled orwell reduced by utilization of a part of the addition current forcharging/discharging the junction capacitance. Furthermore, theremaining ones of the addition currents are used for adding/subtractingan addition power to/from the heating pulse/cooling pulse. Thereby,without increasing the pulse width resolution, it becomes possible toeasily improve the beam-application energy. Accordingly, the laser beamcan be produced with a desired light waveform including the additionpulse.

[0244] Further, according to the seventh embodiment and variantembodiments of the present invention, a pulse width added to the toppulse of a pulse sequence, a pulse width added to the last pulse of thesame, and a pulse width added to other intermediate pulses may be set,separately. Thereby, a form of the front edge part of a record mark, aform of an intermediate part of the same, and a form of a rear edge partof the same can be controlled with sufficient accuracy, and an accuraterecord mark can be formed uniformly.

[0245] Further, according to the seventh embodiment and variantembodiments of the present invention, by determining the width of theaddition pulse according to information before and after the relevantrecord mark, it becomes possible to well control the beam-applicationenergy in consideration of thermal influence of the adjacent recordmarks, without improving the pulse width resolution. Thereby, moreaccurate record mark formation is easily attained.

[0246] Furthermore, according to the seventh embodiment and variantembodiments of the present invention, a pulse width added to the toppulse may be determined from the mark length of a relevant record markas well as the space length of the immediately preceding to the relevantrecord mark, while a pulse width added to the last pulse may bedetermined from the mark length of the relevant record mark as well asthe space length of the immediately subsequent to the relevant recordmark. Thereby, with a simple configuration, it becomes possible to wellcontrol the beam-application energy in consideration of thermalinfluence of the adjacent record marks easily, without improving thepulse width resolution. Thereby, more accurate record mark formation isattained.

[0247] Thus, it becomes possible to achieve high-accuracy record markformation without increasing the resolution of beam-application timeperiod and cooling time period, even for a high-speed recording.

[0248] Further, the present invention is not limited to theabove-described embodiments, and variations and modifications may bemade without departing from the basic concept of the present invention.

[0249] The present application is based on Japanese priorityapplications Nos. 2002-194161 filed on Jul. 3, 2002, 2002-218559 filedon Jul. 26, 2002, and 2003-164054, filed on Jun. 9, 2003, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A light source drive which modulates a lightsource so as to cause the same to emit a light, comprising: a waveformshaping part which corrects a deformation of a light waveform of thelight to be emitted from said light source.
 2. A light source drivewhich modulates a light source so as to cause the same to emit a light,comprising: a superposition current generation part which generates asuperposition current approximately corresponding to acharging/discharging current needed for a capacitance occurring inparallel to said light source for a predetermined time period near atleast one of a rising-up part and a decaying-down part of a waveform ofa drive current for said light source; and an addition/subtraction partwhich adds to or subtracts from the drive current the superpositioncurrent generated by said superposition current generation part.
 3. Thelight source drive as claimed in claim 2, further comprising: asuperposition time control part which controls a superposition timeaccording to said capacitance for which the superposition current isgenerated.
 4. The light source drive as claimed in claim 2, furthercomprising: a superposition current control part which controls thesuperposition current according to said capacitance.
 5. The light sourcedrive as claimed in claim 2, further comprising: a superposition timecontrol part which controls a superposition time according to saidcapacitance for which the superposition current is generated; and asuperposition current control part which controls the superpositioncurrent in the superposition time controlled by said superposition timecontrol part.
 6. The light source drive as claimed in claim 3, wherein:said superposition time control part controls the superposition timeaccording to a change amount of the drive current.
 7. The light sourcedrive as claimed in claim 5, wherein: said superposition time controlpart controls the superposition time according to a change amount of thedrive current.
 8. The light source drive as claimed in claim 4, wherein:said superposition current control part controls the superpositioncurrent value according to a change amount of the drive current.
 9. Thelight source drive as claimed in claim 5, herein: said superpositioncurrent control part controls the superposition current value accordingto a change amount of the drive current.
 10. A light source drive whichmodulates a light source so as to cause the same to emit a light,comprising: an output impedance control part which changes an outputimpedance value of a drive current output part which provides a drivecurrent to said light source, for a predetermined time period near atleast one of a rising-up part and a decaying-down part of a waveform ofthe drive current.
 11. A light source drive which modulates a lightsource so as to cause the same to emit a light, comprising: a MOStransistor connected in parallel with a drive current output part whichoutputs a drive current to said light source; and a voltage control partwhich applies a voltage to a gate of said MOS transistor such that saidMOS transistor enters a linear region for a predetermined time periodnear at least one of a rising-up part and a decaying-down part of awaveform of the drive current.
 12. The light source drive as claimed inclaim 10, further comprising: a time control part which controls saidpredetermined time period.
 13. The light source drive as claimed inclaim 11, further comprising: a time control part which controls saidpredetermined time period.
 14. The light source drive as claimed inclaim 10, further comprising: a resistance value control part whichcontrols said output impedance value.
 15. A light source drive whichmodulates a light source so as to cause the same to emit a light,comprising: a superposition current generation part which generates asuperposition current approximately corresponding to acharging/discharging current needed for a capacitance occurring inparallel to said light source for a predetermined time period near atleast one of a rising-up part and a decaying-down part of a waveform ofa drive current of said light source; an addition/subtraction part whichadds to or subtracts from the drive current the superposition currentgenerated by said superposition current generation part; and an outputimpedance control part which changes an output impedance value of adrive current output part which provides the drive current to said lightsource, for a predetermined time period near at least one of a rising-uppart and a decaying-down part of a waveform of the drive current.
 16. Alight source drive which modulates a light source so as to cause thesame to emit a light, comprising: a superposition signal generation partwhich generates a superposition signal which indicates a predeterminedtime period near at least one of a rising-up part and a decaying-downpart of a waveform of a drive current of said light source; asuperposition current generation part which generates a superpositioncurrent approximately corresponding to a charging/discharging currentneeded for a capacitance occurring in parallel to said light sourcebased on the superposition signal generated by said superposition signalgeneration part; an addition/subtraction part which adds to or subtractsfrom the drive current the superposition current generated by saidsuperposition current generation part; and an output impedance controlpart which changes an output impedance value of a drive current outputpart which provides the drive current to said light source, for apredetermined time period near at least one of a rising-up part and adecaying-down part of a waveform of the drive current.
 17. A lightsource drive which modulates a light source so as to cause the same toemit a light, comprising: a waveform shaping part which corrects adeformation of a light waveform of the light to be emitted from saidlight source; and a waveform shaping time control part which controls atime period for which said waveform shaping part performs a waveformshaping operation.
 18. A light source drive comprising: a light sourcemodulation part which modulates a light source so as to cause the sameto emit a light; a superposition current generation part which generatesa superposition current in a predetermined amount for a predeterminedtime period near at least one of a rising-up part and a decaying-downpart of a waveform of a drive current for said light source; anaddition/subtraction part which adds to or subtracts from the drivecurrent the superposition current generated by said superpositioncurrent generation part; and a superposition time control part whichcontrols said predetermined time period so as to cause it to have apredetermined value.
 19. The light source drive as claimed in claim 18,wherein: said superposition current generation part comprises a firstdelay part which controls a delay amount according to a current amountprovided thereto so as to generate said predetermined time period; saidlight source drive further comprises: an oscillation part whichcomprises a second delay part having a characteristic which isequivalent to said first delay part; a delay time control part whichcontrols a current provided to said oscillation part so that theoscillation frequency of said oscillation part becomes a predeterminedfrequency; and a part which determines the current provided to saidfirst delay part of said superposition current generation part based onthe current value controlled by said delay time control part.
 20. Alight source drive comprising: a light source modulation part whichmodulates a light source so as to cause the same to emit a light; anoutput impedance control part which changes an output impedance value ofsaid light source modulation part for a predetermined time period nearat least one of a rising-up part and a decaying-down part of a waveformof a drive current for said light source; and a time control part whichcontrols said predetermined time period so as to cause it to have apredetermined value.
 21. The light source drive as claimed in claim 20,wherein: said output impedance control part comprises a first delay partwhich controls a delay amount according to a current amount providedthereto so as to generate said predetermined time period; and said lightsource drive further comprises: an oscillation part which comprises asecond delay part having a characteristic which is equivalent to saidfirst delay part; a delay time control part which controls a currentprovided to said oscillation part so that the oscillation frequency ofsaid oscillation part becomes a predetermined frequency; and a partwhich determines the current provided to said first delay part of saidoutput impedance control part based on the current value controlled bysaid delay time control part.
 22. A light source drive comprising: alight source modulation part which modulates a light source so as tocause the same to emit a light; a superposition current generation partwhich generates a superposition current in a predetermined amount for afirst predetermined time period near at least one of a rising-up partand a decaying-down part of a waveform of a drive current for said lightsource; an addition/subtraction part which adds to or subtracts from thedrive current the superposition current generated by said superpositioncurrent generation part; an output impedance control part which changesan output impedance value of said light source modulation part for asecond predetermined time period near at least one of a rising-up partand a decaying-down part of a waveform of a drive current for said lightsource; and a time control part which controls said first predeterminedtime period and said second predetermined time period so as to causethem to have predetermined values.
 23. The light source drive as claimedin claim 22, wherein: said superposition current generation partcomprises a first delay part which controls a delay amount according toa current amount provided thereto so as to generate said firstpredetermined time period; said output impedance control part comprisesa second delay part which has a characteristic equivalent to that ofsaid first delay part of said superposition current generation part, andthereby generates said second predetermined time period; and said lightsource drive further comprises: an oscillation part which comprises athird delay part having a characteristic which is equivalent to saidfirst delay part; a delay time control part which controls a currentprovided to said oscillation part so that the oscillation frequency ofsaid oscillation part becomes a predetermined frequency; and a partwhich determines the current provided to said first delay part of saidsuperposition current generation part and the current provided to saidsecond delay part of said output impedance control part based on thecurrent value controlled by said delay time control part.
 24. The lightsource drive as claimed in claim 19, further comprising: a communicationpart which performs a communication operation for data and command basedon a clock signal having a predetermined frequency; and a part detectingthe oscillation frequency of said oscillation part by counting thenumber of pulses output from said oscillation part during apredetermined frequency detection period generated based on said clocksignal.
 25. The light source drive as claimed in claim 21, furthercomprising: a communication part which performs a communicationoperation for data and command based on a clock signal having apredetermined frequency; and a part detecting the oscillation frequencyof said oscillation part by counting the number of pulses output fromsaid oscillation part during a predetermined frequency detection periodgenerated based on said clock signal.
 26. The light source drive asclaimed in claim 23, further comprising: a communication part whichperforms a communication operation for data and command based on a clocksignal having a predetermined frequency; and a part detecting theoscillation frequency of said oscillation part by counting the number ofpulses output from said oscillation part during a predeterminedfrequency detection period generated based on said clock signal.
 27. Thelight source drive as claimed in claim 24, wherein: said communicationpart performs a communication operation of transferring the data andcommand in serial in an order of an address and the data based on theclock signal at the predetermined frequency; and said predeterminedfrequency detection period comprises a data communication period in casesaid address indicates a detection of a frequency of a high-frequencysignal.
 28. The light source drive as claimed in claim 25, wherein: saidcommunication part performs a communication operation of transferringthe data and command in serial in an order of an address and the databased on the clock signal at the predetermined frequency; and saidpredetermined frequency detection period comprises a data communicationperiod in case said address indicates a detection of a frequency of ahigh-frequency signal.
 29. The light source drive as claimed in claim26, wherein: said communication part performs a communication operationof transferring the data and command in serial in an order of an addressand the data based on the clock signal at the predetermined frequency;and said predetermined frequency detection period comprises a datacommunication period in case said address indicates a detection of afrequency of a high-frequency signal.
 30. The light source drive asclaimed in claim 24, wherein: said communication part performs acommunication operation of transferring the data and command in serialin an order of an address and the data based on the clock signal at thepredetermined frequency; and said predetermined frequency detectionperiod comprises the address and data communication period.
 31. Thelight source drive as claimed in claim 25, wherein: said communicationpart performs a communication operation of transferring the data andcommand in serial in an order of an address and the data based on theclock signal at the predetermined frequency; and said predeterminedfrequency detection period comprises the address and data communicationperiod.
 32. The light source drive as claimed in claim 26, wherein: saidcommunication part performs a communication operation of transferringthe data and command in serial in an order of an address and the databased on the clock signal at the predetermined frequency; and saidpredetermined frequency detection period comprises the address and datacommunication period.
 33. An optical information recording method offorming a record mark on a recording medium by applying a light emittedfrom a light source in a form of a pulse series, comprising the stepsof: a) adding a pulse of predetermined power for a predetermined timeperiod after near a rising-up part of each of at least some pulses ofthe pulse series; and b) controlling a pulse width of the pulse thusadded so as to control the formation of the record mark.
 34. An opticalinformation recording method of forming a record mark on a recordingmedium by applying a light emitted from a light source in a form of apulse series, comprising the steps of: a) adding a first addition pulseof predetermined power for a predetermined time period after near arising-up part of each of at least some pulse of the pulse series; b)adding a second addition pulse of predetermined power for apredetermined time period after near a decaying-down part of each ofsaid at least some pulses of the pulse series; and c) controlling apulse width of the first addition pulse thus added and a pulse width ofthe second addition pulse thus added so as to control the formation ofthe record mark.
 35. An optical information recording method of forminga record mark on a recording medium by applying a light emitted from alight source in a form of a pulse series, comprising the steps of: a)adding or subtracting a predetermined addition current to a drivecurrent of said light source for a predetermined time period after neara rising-up part or a decaying-down part of each of at least some pulsesof the pulse series; b) determining the predetermined time for theaddition current such that a part of the addition current isapproximately appropriated for charging/discharging a capacitanceoccurring in parallel to said light source and the remaining part ofsaid addition current is used as an addition power to be applied so asto control the formation of the record mark.
 36. The optical informationrecording method as claimed in claim 33, wherein: a pulse width appliedfor a top pulse of the pulse series, a pulse width applied for a lastpulse of the pulse series and a pulse width applied for the otherintermediate pulses are set respectively.
 37. The optical informationrecording method as claimed in claim 34, wherein: a pulse width appliedfor a top pulse of the pulse series, a pulse width applied for a lastpulse of the pulse series and a pulse width applied for the otherintermediate pulses are set respectively.
 38. The optical informationrecording method as claimed in claim 35, wherein: a pulse width appliedfor a top pulse of the pulse series, a pulse width applied for a lastpulse of the pulse series and a pulse width applied for the otherintermediate pulses are determined respectively.
 39. The opticalinformation recording method as claimed in claim 33, wherein: the pulsewidth of each addition pulse thus added is determined according tolengths of information occurring preceding and subsequent to a relevantrecord mark.
 40. The optical information recording method as claimed inclaim 34, wherein: the pulse width of each addition pulse thus added isdetermined according to lengths of information occurring preceding andsubsequent to a relevant record mark.
 41. The optical informationrecording method as claimed in claim 35, wherein: the pulse width ofeach addition pulse thus added is determined according to lengths ofinformation occurring preceding and subsequent to a relevant recordmark.
 42. The optical information recording method as claimed in claim36, wherein: the pulse width of the addition pulse added to the toppulse is determined according to the mark length of the relevant recordmark and the immediately preceding space length, and the pulse width ofthe addition pulse added to the last pulse is determined according tothe mark length of the relevant record mark and the immediatelysubsequent space length.
 43. The optical information recording method asclaimed in claim 37, wherein: the pulse width of the addition pulseadded to the top pulse is determined according to the mark length of therelevant record mark and the immediately preceding space length, and thepulse width of the addition pulse added to the last pulse is determinedaccording to the mark length of the relevant record mark and theimmediately subsequent space length.
 44. The optical informationrecording method as claimed in claim 38, wherein: the pulse width of theaddition pulse added to the top pulse is determined according to themark length of the relevant record mark and the immediately precedingspace length, and the pulse width of the addition pulse added to thelast pulse is determined according to the mark length of the relevantrecord mark and the immediately subsequent space length.
 45. An opticalinformation recording apparatus for forming a record mark on a recordingmedium by applying a light emitted from a light source in a form of apulse series, comprising: an addition current generation part whichgenerates an addition current in a predetermined value for apredetermined time period after near a rising-up part of each of atleast some pulses of the pulse series; an addition time setting partwhich determines said predetermined time period for the additioncurrent; and an adding part which adds the addition current to a drivecurrent for said light source.
 46. An optical information recordingapparatus for forming a record mark on a recording medium by applying alight emitted from a light source in a form of a pulse series,comprising: an addition current generation part which generates anaddition current in a predetermined value for a predetermined timeperiod after near a rising-up part or a decaying-down part of each of atleast some pulses of the pulse series; an addition time setting partwhich determines said predetermined time period for the additioncurrent; and an adding/subtracting part which adds/subtracts theaddition current to/from a drive current for said light source.
 47. Anoptical information recording apparatus for forming a record mark on arecording medium by applying a light emitted from a light source in aform of a pulse series, comprising: an addition current generation partwhich generates an addition current in a predetermined value for apredetermined time period after near a rising-up part or a decaying-downpart of each of at least some pulses of the pulse series; an additiontime setting part which sets the predetermined time for the additioncurrent such that a part of the addition current is approximatelyappropriated for charging/discharging a capacitance occurring inparallel to said light source and the remaining part of said additioncurrent is used as an addition power to be applied; and anadding/subtracting part which adds/subtracts the addition currentto/from a drive current for said light source.
 48. The opticalinformation recording apparatus as claimed in claim 45, wherein: saidaddition part setting part determines a pulse width of the additionpulse applied for a top pulse of the pulse series, a pulse width of theaddition pulse applied for a last pulse of the pulse series and a pulsewidth of the addition pulses applied for the other intermediate pulsesrespectively.
 49. The optical information recording apparatus as claimedin claim 46, wherein: said addition part setting part determines a pulsewidth of the addition pulse applied for a top pulse of the pulse series,a pulse width of the addition pulse applied for a last pulse of thepulse series and a pulse width of the addition pulses applied for theother intermediate pulses respectively.
 50. The optical informationrecording apparatus as claimed in claim 47, wherein: said addition partsetting part determines a pulse width of the addition pulse applied fora top pulse of the pulse series, a pulse width of the addition pulseapplied for a last pulse of the pulse series and a pulse width of theaddition pulses applied for the other intermediate pulses respectively.51. The optical information recording apparatus as claimed in claim 45,wherein: said addition part setting part determines the pulse width ofeach addition pulse added according to lengths of information occurringpreceding and subsequent to a relevant record mark.
 52. The opticalinformation recording apparatus as claimed in claim 46, wherein: saidaddition part setting part determines the pulse width of each additionpulse added according to lengths of information occurring preceding andsubsequent to a relevant record mark.
 53. The optical informationrecording apparatus as claimed in claim 47, wherein: said addition partsetting part determines the pulse width of each addition pulse addedaccording to lengths of information occurring preceding and subsequentto a relevant record mark.
 54. The optical information recordingapparatus as claimed in claim 48, wherein: said addition part settingpart determines the pulse width of the addition pulse added to the toppulse according to the mark length of the relevant record mark and theimmediately preceding space length, and determines the pulse width ofthe addition pulse added to the last pulse according to the mark lengthof the relevant record mark and the immediately subsequent space length.55. The optical information recording apparatus as claimed in claim 49,wherein: said addition part setting part determines the pulse width ofthe addition pulse added to the top pulse according to the mark lengthof the relevant record mark and the immediately preceding space length,and determines the pulse width of the addition pulse added to the lastpulse according to the mark length of the relevant record mark and theimmediately subsequent space length.
 56. The optical informationrecording apparatus as claimed in claim 50, wherein: said addition partsetting part determines the pulse width of the addition pulse added tothe top pulse according to the mark length of the relevant record markand the immediately preceding space length, and determines the pulsewidth of the addition pulse added to the last pulse according to themark length of the relevant record mark and the immediately subsequentspace length.